Vladimir Bukanov. Russian Gemstones Encyclopedia
QUARTZ, GROUP: (QUARTZ, AMETHYST, ROSE QUARTZ, CHALCEDONY, OPAL, AVENTURINE)
QUARTZ group (Quarz—Quartz—Кварц) (Agricola, G. 1529). Known from antiquity, the origin of the name is uncertain; possibly from West Slav dialect “kwardy” corresponding to Czech “tvrd˘” – hard. The name quartz appears to have replaced the term crystal or rock crystal toward the end of the 18th cent. Here also main gemstones from the quartz group are described: amethyst, rose quartz, chalcedony, opal and aventurine.
Composition & Properties. Oxide – SiO2, trigonal system. Admixtures: aluminum (Al3+), lithium (Li+), sodium (Na+), and hydrogen (H+). Hardness 7. Density 2.65. Cleavage non-perfect in two directions. Glass luster, dull one in aggregates. Fragile. Quartz is one of widespread minerals in the Earth’s crust, because it is a rock-forming mineral for many magmatic, metasomatic, metamorphic and sedimentary rocks. Among the jewelry-ornamental varieties of quartz they distinguish three groups according the special features of crystal structure: 1) clear crystal – rock crystal and colored varieties of quartz crystals: amethyst, ametrine, rosa quartz and smoky quartz, morione, citrine, prasiolite; 2) cryptocrystalline – amorphous opal, chalcedony and its varieties chrysoprase, plasma, chert; 3) massive varieties – white veined quartz, amethyst-like quartz, rose quartz and quartz-perelift. Then, cristobalite are also described – it’s a polymorphous modification of quartz, which takes part in the content of gemstones, and rocks of quartz content – ornamental stones.
In crystals of quartz there are often seen multicolored zone and sector coloring. Those are smoky quartz with citrine and its variety – greenish-yellow vertine with zones of smoky color, and ametrine – with amethyst and citrine color at different sectors of growing of different sides. Changing of color in quartz between differently colored zones can be gradual or contrast ones. The exclusion is almost black morione, which differs from smoky quartz with its non-transparency, although the fact that in the outer zones of growing it can have also transparent parts with smoky and more rarely with amethyst coloring. In bright zones of citrine color of quartz it is seen the specific effect of blue rays. It is obvious under the slanting lighting as fine net of crossing rays, which look like rain. This effect is connected with the system of the thinnest cracks, which are parallel to the sides of rhombohedron. They appear because of the difference in parameters of crystal lattice in differently colored zones. Blue rays are obvious as a result of light dispersing in these cracks.
Inclusions in transparent quartz more or less often have ornamental character. Such varieties of quartz look especially nice after facet. Among them, there are quartz hair stone and landscape quartz with mineral inclusions. The first mention about such quartz we can find in the works by Ibn Sina or Avicenna (980-1033), who described crystals of bellor – rock crystal with inclusions in the shape of green bow and a hyacinth flower. Among the needle minerals, which produce landscape quartz and quartz hair stone, we should mention aikinite or acicular bismuth, actinolite, astrophyllite, boulangerite, hedenbergite, goethite, cosalite, millerite, rutile, sillimanite, tourmaline, chlorite, epidote and others. Inclusions of fine needles of green tourmaline and actinolite in rock crystal are called Thetis hair stone. Earlier transparent quartz with inclusions rutile and schorl jewelers on some reasons named wollastonite. Entangled-fibrous inclusions of rutile in quartz are also called – Venus hair stone, and in the East – Prophet beard hairs, but more thick needles are called – d’Amour flèche. The presence of long plates-inclusions of golden rutile or reddish lepidocrocite became the reason for another name of hair stone – straw quartz. Inclusions of fine-dispersed rutile give dark blue color in blue quartz. Variety close to quartz hair stone is blue quartz (See: Synonyms) with inclusions of blue amphibole-asbestos – crocidolite, as well as tourmaline. Such quartz sometimes is called inaccurately blue moonstone. Massive quartz varieties of riebeckite asbestos have trade name – rhodusit asbestos. Parallel-fibrous aggregates replaced with quartz in cabochons usually display the effect of cat’s-eye. Its color depends on: goethite – in reddish-yellow binghamite or dark brownish tiger iron; actinolite and cummingtonite asbestos – in green quartz cat’s-eye; crocidolite – in blue quartz hawk’s-eye, quartz falcon’s-eye, crocidolite cat’s-eye or South African cat’s-eye. In the U.S.A. quartz falcon’s-eye is called blue tiger’s-eye and silky stone. Bluish hawk’s-eye after the oxidation of crocidolite up to goethite and lepidocrocite receives brownish color and is called crocidolite quartz and if it is chatoyancy in it – tiger’s-eye or lion’s-eye. Under the artificial or natural annealing of tiger’s-eye goethite transfers to hematite and the stone receives reddish-brown color and is called ox-eye. Hawk’s-eye with additional colored stripes is called zebras-eye. Intermediate variety according its color between tiger’s-eye and falcon’s-eye in greenish-yellow tones has a trade name wolf ’s-eye stone or wolf ’s-eye. In German gemology there is a general name for jewelry varieties of quartz with effects like the effect of cat’s-eye – pupillenquarz.
Small mineral inclusions in quartz produce such varieties as aventurine quartz (See aventurine). In green buddstone, prase or emerald prase – actinolite, epidote, chlorite, pyroxenes or celadonite can be represented. In red-brown iron quartz – hematite or goethite (See syn.). Carmasul or rubasse is quartz with inclusions of hematite, malachite and chrysocolla. Microcrystalline inclusions of rutile, tourmaline, magnetite, ilmenite, apatite, zoisite or gas-liquid inclusions in quartz give opalescence with light blue or dark blue tone in reflected light, because of light diffusion – so called the effect of Tindal. It is known such opalescent rose quartz with asterism – starolite. In milky-white quartz – hyaline opalescence is produced with fine cracks. Sometimes quartz with thick rare needles of tourmaline was faceted like brilliant, so that one needle was placed in the center of a table facet perpendicular to its surface. In a cut stone a reflection of such needle from facets of pavilion looks like a star. Among the other optical effects of quartz, we should mention the play of color, which depends on small cracks in a transparent crystal. Interference of light in these cracks produce iridescence, and quartz is called rainbow quartz and some other way (See syn.). Massive veined quartz attracts attention as an ornamental stone only if it has decorative elements. At first, it is color: according it they classify bluish-transparent icy quartz, green chrysoprase quartz, rose quartz and amethyst-like quartz. Quartz colored with oxides of iron along its cracks in yellowish and red-brown tone is called iron quartz, Eisenkiesel, Germ. or ferrous chert. Because of its intensive color, it can be not very translucent up to non-transparent. Other examples of ornamental milky-white veined quartz are also connected with mineral inclusions. Among them, there are gold quartz with native gold in grains and veins; variscite quartz with green variscite; blue quartz with inclusions of azurite, tourmaline, lazulite; stellerite with chrysocolla; reddish or rose quartz with inclusions of cinnabar, known as myrickite or cinnabery jasper; dark blue dumortierite quartz or Californian lapis with dumortierite. The last one changes its color from intensive dark blue to greenish-blue and to violet-blue and rose with the decrease of concentration of needle inclusions and their size.
Among the morphological varieties of quartz there are interesting pseudomorphs on datolite – haytorite, as well as forms of splinted growing – artichoke quartz and gradual growing of sides – Babylon quartz or Babbel (babel) quartz and fensterquarz. We should also mention Japan twins of quartz, which are highly valued by collectors. Such almost perpendicular joint crystals can reach substantial size. In the Mineral. Museum SPb. Univ. there is such Japan twin of quartz from the Pamirs Mts., 30 cm. in cross-section. Another rare variety of collection quartz is twisted quartz in crystals up to 25 cm. long on the axis of the second grade – gwindel.
Cristobalite, which was named after the discovery location near San Crystobal, the Chiapas State, Mexico, is one of the widespread high-temperature modifications of quartz. It is difficult to differ it from the other modifications, but it has a bit lower hardness 6.5 and density 2.3. Usually it is represented with colorless or milky-white fine-grained aggregates, sphaerolites or fibrous variety – lussaite. In Japan, there are many deposits with cristobalite in the shape of white sphaerolites up to 10 cm. in cross-section. Rather often cristobalite contains mineral admixtures. It is in the content of agate, chalcedony and cristobalite opal, non-transparent variety of opal – menilite, woody tin, silicified wood and siliceous sinter. In snowflake obsidian, landscape rhyolite and in metallurgy cristobalite scoria produces ornamental sphaerolites, up to 2.5 cm. in size. In glass imitations, in the shape of white spots, it makes blue gold glass more decorative. At first lussaite was described in veins of bitumen near Lussate, France. There are also known its findings in serpentinite of Western Moravia, Czech, and in the land Styria, Austria.
Ornamental rocks. Perelift received its name because of its iridescent color from the Old Russ. synonym of chalcedony – perelifty. Earlier it was classified as one of agate. This jewelry-ornamental stone is built with cryptocrystalline druses and parallel-columnar quartz aggregates, which produce massive veined rock with fine layers of corrugated and brecciated structure. Its bedding is connected with crustification admixtures of dickite, sulfides and hydroxides of ferrous. Usually it is pale-yellow, light blue-gray with gradual iridescent – changing of tone. Intensity of its color depends on the grade of oxidation of admixing minerals in hypergenous conditions. In the Urals, in the upper part of the Shaitan deposit, where this stone is extracted, wavy fine-stripped. color is obvious. It makes the stone an ornamental one. In the low part it is not so obvious, but it can be strengthened with thermal processing, during which iron (Fe2+) in admixtures is oxidized to Fe3+.
Quartzite is a rock of metamorphic origin, massive structure, mainly quartz content with quartz cement. This solid fine-grained rock is easy polished; it is known as facing stone; some ornamental varieties of it are used for stone carving. Among them there are raspberry-red – Shoksha quartzite, rose – Beloretskiy quartzite and red-brown spotty – Taganai quartzite. The most part of ornamental quartzites has bright color because of mineral admixtures. Ferrous quartzite has its own name – jaspillite. In Brazil iron quartzite is called itabirites. Quartz conglomerate is rock of the same type as quartzite according the conditions of its forming, but it is more megagrained and often has polymineral content. Its multicolored varieties are used sometimes as a facing stone for large objects, like tables and others.
Quartz sandstone is a weakly cemented rock of sedimentary origin. Its ornamental variety is copper sandstone of green and bluish-green color with inclusions of chrysocolla, malachite and turquoise. In the U.S.A., black sandstone is known with cement of noble opal, which gives it the effect of iridescence, that’s why it is used as an ornamental stone. In picture sandstone there are patterns, which are seen on some split surfaces, that’s why it is used as a facing stone. Limnoquartzite from Slovakia is another variety of sandstone; it is fine-grained sedimentary rock, produced in volcano regions, in shallow basins of thermal sources. It is characterized with stripped pattern of different colors in layers up to 20 cm. thick; it is used as a facing stone and more rarely as an ornamental stone.
Diatomite is a sedimentary rock, which consists of cherty skeletons of sea creatures: diatomeias, radiolarians, spongies and others. It is used as fine abrasive material for processing of stone plastics.
Deposits. Quartz is produced at deposits of different genesis. The mostly widespread are granite pegmatites and hydrothermal veins composed with grained quartz. They often have cavity of different size mineralized geodes and pocket. As a rule, rock crystal in these cavity coexists with smoky quartz, citrine, and not rarely also with amethyst. Jewelry-ornamental varieties of quartz usually are extracted as additional material at deposits of piezooptic quartz and in ore veins. In effusive rocks they find amygdales of chalcedony with quartz filling. Metasomatic rocks are represented with ornamental silicification variety, such as quartzite, quartz conglomerate, hornstone, siliceous schist and jasper. During serpentinization of the main rocks veins of transparent icy quartz are formed. Among sedimentary rocks quartz is a forming mineral for diatomites, limnoquartzites, cherts and sandstones. Inside them, quartz crusts are formed with small crystals of Marmarosch diamond type (See App. 12). Industrial deposits of quartz, represented with pegmatites and hydrothermal veins, are concentrated into crystal-containing provinces. In less quantity crystals of quartz can be found in alpine veins, ore veins and skarns.
In Russia, there are two large rock crystal-containing provinces: the Aldan – in the southern part of Yakutia, also Urals – with subprovinces in the South, Middle and Subpolar Urals Mts.. In the Subpolar Urals Mts. there are hundreds of small deposits of rock crystal, among the biggest ones with industrial reserves there are: on the eastern slope – the deposits Dodo, opened in 1935, and Puiva, discovered a bit later; on the western slope – the deposits Pelingichey III, opened in 1952, and Zhelannoye, opened in 1955. In 1946, at the South Urals the largest Astaf’evskoye rock crystal deposit was discovered, near Magnitogorsk. There are Japanese twins up to 42x35 cm. in size, 11.5 kg. In the same region, near Orsk, the Terensay deposit is situated, in 1966, a quartz crystal 170 cm. long, 184 kg., was found there. In the northern part of the Irkutsk Region, crystals of quartz in mica-pegmatites of the Mamsko-Vitimskiy Dist. are found and in East Transbaikalia – in pegmatites with gemstones. In the southern part of Yakutia, in the Aldan crystal-containing provinces, industrial deposits of quartz are known on the Aldan River Valley – there are Suon-Teet and Perekatnoye. Japanese twins up to 15 cm., crystals with inclusions of hematite, which gives the effect of aventurescence, were found there. In the Primorskiy Region, at the Dal’negorskoye deposit, in cavity among skarns they found Japanese twins quartz up to 2.5 cm. in size. In the northern part of Yakutia, in the axis part of the Verkhoyanskiy Ridge, there is a significant quantity of crystal-containing veins. On the Chukchi Penin. rock crystal was extracted as additional material in ore veins together with gold. In the Ukraine, crystal-containing pegmatites in the Volodarsk-Volhynskoye pegmatite field, Zhitomir Region, were exploited. In these pegmatites size of miarolitic cavity reaches 10 m. and even more, and their volume 40 m3. , more rare up to 250 m3. Cavity is filled with crystals of morione and smoky quartz, up to 1000 kg and sometimes and up to 3,2 ton weight. In Central Kazakhstan quartz deposits are connected either with rock crystal-containing veins – Aktas deposit or with pegmatites – Kent deposit. In Tadzhikistan, in the West and East Pamirs Mts., druses cavity contained considerable amount of rock crystals. They consist of Japanese twins of quartz. Such twin, 21x29 cm. in size, 6 kg., at the Gudzivas deposit was found, West Pamirs. In East Mongolia rock crystal is extracted at the pegmatites deposits of the Hantay crystal-containing field. In Romania Japanese twins of quartz, up to 10 cm. in size, were found at the Ocna de Fier deposit. In the alpine veins, of unique collection material is extracted, including rock crystal. From these regions, mainly Switzerland and France, crystals of gwindel quartz, Japanese twins, and rock crystals with ornamental inclusions of different minerals are coming to the jewelry market. On Madagascar, there are more than 30 large deposits, where quartz crystals in pegmatites and hydrothermal veins were extracted. They have been being extracted since the 17th cent. They are concentrated mainly in the north-eastern and central parts of the island. The largest deposits are Crystallina and Beombiaty, Anjoma-Ramartina region. Rock crystal is represented there with crystals up to 7 m. long and 700 kg. There are also smoky quartz, citrine, blue quartz, aventurine quartz and amethyst.In South Africa, large deposits of rock crystal are in Angola and Zambia. In the north-eastern part of Zimbabwe (form. South Rhodesia), near Mtoko, transparent light blue-white quartz with beautiful iridescence is known; it is called Rhodesian moonstone. In Mozambique, in the Alto Ligonha Region, in pegmatites they found quartz crystals up to 1 m. long. Among the countries of Asia, China takes a special part from the point of view of deposits of rock crystal. There are Eastern and Western crystal-containing provinces and the Yanzyaoling deposit on the Hainan Is. Here are pieces of rock crystal with the obvious effect of blue rays, and in the Hunan Prov. crystals of quartz hair stone with needle inclusions of cosalite and so called artichoke quartz, quartz with splitting shape of crystals was found. In India, in the Andhra-Pradesh State, quartz was extracted at the deposits of the Nellur pegmatite field – Sakhramine and others. In Myanmar, the Sakanga quartz deposit was exploited. In Japan, quartz was extracted at the Kimpu-San deposit, Yamanashi Pref.; and at the Otomo mine, Iwate Pref., quartz crystals up to 1 m. long were found, as well as Japanese twins of quartz, 45 cm. in cross-section. On the Naru-shima Is., Nagasaki Pref., numerous Japanese twins of quartz, up to 1 cm. long, were found.
Brazil takes the first place in the world in the development of rock crystal deposits. In the eastern part of the country its deposits are connected mainly with pegmatites. They are found from Fortaleza in the north São Paolo State, to in the south one. In the Goiás State, at the Manchao Felipe mine the biggest quartz crystal in Brazil – 6.1 m., 44 ton. was found. In Minas Gerais, at the Curvello mine they found Japanese twins of quartz up to 25 cm. in cross-section. In the western part of Brazil there are also large deposits of rock crystal: Cristalina, Goiás; Longo Pit and Cavalcanti Tocantins, Bahia, and others. In this area the Central zone with deposits Seti Pagos, Salitre and others is situated. In the U.S.A. deposits of rock crystal in Arizona are exploited, where crystals more than 500 kg. were extracted, including perfect collection druses; also at the Holland mine, Santa Cruz Co., their size reached 30 cm. In Arkansas, rock crystal in Coleman Crystal mine was extracted; and at the Collier Creek mine, Montgomery Co., where Japanese twins of quartz up to 15 cm. were found. In the New York State, Herkimer Co., quartz crusts, composed with small crystals are found; they have a trade name Herkimer diamond. The similar deposits are in the states of New Jersey, Colorado and others. Similar quartz crusts are known widely in other countries (See App. 12). In Peru, Japanese twins of quartz at deposits of rock crystal are found: Pampa Blanca, Ica Dept.; La Tentadora, Huancavelica Dept.; Huallapon, Ancash Dept. Also they were found in New Caledonia.
Quartz hair stone. Its first findings in Russia were made on Volk-Ostrov (Wolf Is.) in the Onega Bay of the White Sea. There, in the contact zone of shungite slates and diabases geodes with crystals of amethyst hair stone, enriched with inclusions of goethite, are found. In the 18th cent., such crystals were in fashion among jewelers under the name of onegit. On the east slope of the Subpolar Urals Mts. quartz hair stone with rutile at the deposits of rock crystal was found: Puiva, Central Patok, Feiko-Shor. On the west slope it was found at the deposits Central Lapcha, Chioln-Iz, Verkhniy Parnuck, Skalistoye. At the Zhelannoye deposit crystals of quartz hair stone with ornamental inclusions of rutile, tourmaline, boulangerite and actinolite are not rare. Findings of quartz hair stone with cosalite are registered at hydrothermal deposits of the Middle Urals – at the Beresovskiy mine and at the Lobachiovskaya mine; in the South Urals – at the Kochkar’ deposit. They are also described at tungsten deposits in Transbaikalia – Bukuka and Sokhondo; and in the Primorskiy Region – at the Zabytoye deposit near the city of Dal’negorskoye. Inclusions of boulangerite in quartz are known also in the Ukraine, at the Esaulovka deposit in the Nagolnyi Ridge, Donetsk Region. In Central Kazakhstan, similar findings of cosalite in quartz are known at the Karaoba deposit; in North Tadzhikistan – at the Adrasman mine, Khujand (Khodzhent) Dist. Besides, there are of special interest for collectors’ crystals of quartz with inclusions of brookite, hematite, ilmenite, paragonite, sericite and chlorite. In the Museum Earth, State Moscow Univ. a flat crystal is exhibited; it is from the Pyramid deposit, Subpolar Urals Mts., 40 cm. long, with inclusions of rutile and sericite, which compose a landscape of winter taiga. In the Sablya Mt. there is a deposit of prase, the color of which depends on inclusions of actinolite. In the Middle Urals, in pegmatites veins of the Murzinsko-Aduiskiy field., near Yekaterinburg, quartz crystals contain inclusions of epidote and actinolite. Milky-white veined quartz with inclusions of tourmaline also was used as ornamental material. In the region of Nizhniy Tagil, at the Gorbunovskoye deposit, prase was extracted; there were quartz crystals enriched with inclusions of actinolite. In the South Urals, quartz hair stone at the Svetlinskoye deposit of rock crystal was found, where its crystals with red and black needles of rutile reached 12 cm. in length. At the Astaf’evskoye deposit, transparent crystals of quartz with needle inclusions of pyrite and gersdorffite were found. In the Primorskiy Region, at the Sinerechenskoye deposit there are findings of green quartz prase with inclusions of actinolite. In Georgia, in the Kazbek Mt., crystals of rock crystal contain inclusions of bitumen. In Kazakhstan, on the Mangyshlak Penin. (now Tüpqaraghan Tübegi), near Tauchik, in iron-ore manifestation of goethite crystals of quartz in geodes are multicolored – amethyst, citrine colored and colorless. On the surface they are filled with needle inclusions of hematite and goethite, which give them reddish-brown tone. At the Aktas deposit crystals of rock crystal often contain inclusions of epidote, and at the Quara Oba deposit – inclusions of cosalite and rhodochrosite In Uzbekistan, in the Toshkent Region, near the border with Kazakhstan, quartz hair stone in quartz and feldspar veins of the Maydantal deposit was found. Quartz hair stone is not only with inclusions of rutile, but also with actinolite in crystals up to 15 cm. long, there. In Greece, on the Serifos Is., they find quartz crystals, green of inclusions of hedenbergite. In South Africa, at the Messina mine a rare case of inclusions of papagoite in a crystal of quartz was registered. In Australia, at the Mt. Isa deposit, Queensland, findings of quartz crystals with inclusions of needled boulangerite were described.
In Brazil, in Minas Gerais, rock crystal with inclusions of tourmaline is extracted at deposits of the Governador-Valadares region; it is called – tourmaline quartz. There is also rare found blue-violet quartz cat’s-eye with inclusions of lithium amphibole – holmquistite. In the region of Diamantina, at the Serra do Cabral deposit quartz with inclusions of chlorite is extracted. In the Bahia State, rock crystal-containing veins serve as an industrial source of quartz hair stone with rutile, in the Ibiajara region. In Brazil, also black quartz in the shape of two-sided crystals was found – up to 50 cm. long, with lustrous facets; it is enriched with carbon inclusions.
Inclusions of fine plates of hematite lead to appearance of strong luster and rose-red tone in crystals of strawberry quartz from the Chihuahua State, Mexico. Plates of hematite in such quartz are placed along the facets of the upper part of a crystal, leaving parts along the edges free. Because of this splitting a crystal near the upper part, perpendicular to the long axis of a crystal, a man can receive a light-colored star on reddish background with flakes of hematite. Recently, similar false star quartz is found in Kazakhstan, at the Zhairem deposit, near Chimkent (now Shymkent). This effect is called pseudosterism or false asterism (See emerald). Another example of the similar effect appears after the full replacement in quartz of ilmenite inclusions with needles of rutile in the shape of six-radial star. In Brazil, crystals with such plates of ilmenite are called Ryo star. In star quartz micro inclusions of rutile, ilmenite or hematite’s leads to asterism in the shape of three or six-radial star, moving in reflected light. In milky-white star quartz from Sri Lanka asterism with 12-radial star depends on inclusions of the thinnest needles of sillimanite. Blue quartz with inclusions of rutile is found at deposits of India, near Kälächändi, Orissa State; and in Namibia. In the U.S.A., in California, in pegmatites of Pala, at the Katerina deposit blue quartz, enriched with the smallest inclusions of tourmaline, is found. There, in quartz veins among rhyolites also blue quartz, enriched with fine needles of dumortierite is found. Such blue dumortierite quartz is typical for deposits of Arizona. In Nevada, in the region of Rochester, both blue dumortierite quartz and red jade are known. In Mexico, blue dumortierite quartz with white spots is extracted at the Guadalkasara deposit, San Luis Potosí State.
Smoky quartz is found and extracted together with rock crystal and citrine. It is often called rauchtopas. But this term is not recommended by CIBJO. At deposits of Scotland, in the Cairngorm Mts., there is smoky quartz of brownish tone. After the discovery location it is called cairngorm. In Russia, deposits of rock crystal and citrine are found in the Urals and in Yakutia, at the Perekatnoye deposit. In the North Urals the Ol’chovochnoye deposit of natural citrine was discovered. Among the other countries it is found in Hungary, in France in Dauphin Dept., Alps-de-Haute-Prov.; in Scotland on the Arroan Is. In Spain, citrine was found together with amethyst in the provinces de Salamanca and de Córdoba, where its crystals reached 1 kg. Findings of citrine are known on Madagascar and in Zimbabwe. In Brazil, in the Rio Grandi do Sul State; at the Rio Piani deposit, its crystals reach 18 cm. in length. From Brazil to the world jewelry market such stones come as citrine, received with the method of annealing from amethyst, under the trade name – Rio Grande topaz or Bahia topaz.
Prasiolite – green quartz of natural color is found in quartz veins of Brazil, an also in the U.S.A. – at the border between Nevada and California. There its crystals reach 6 cm. in length, that’s why the biggest cut stones from them were not more than 20 ct. Such prasiolite was also found in Poland, in agate geodes of Lower Silesia, near Wroclaw. In India, a new variety of olive-green tone was opened. It is transparent quartz crystals up to 7 cm. long, with clear dichroism from yellow-green to green color. There is information about cut of green quartz from India, up to 80 ct. Usually prasiolite is received with the method of annealing of amethyst crystals, which are extracted in Brazil, at the Montezuma deposit, Minas Gerais; and in the U.S.A. at the Tour Peaks deposit, Arizona. Among the other ornamental varieties of quartz in Russia we should mention quartz cat’s-eye. In Karelia, it is found as fine veins together with dendrites of native copper in basalts of the Kondopoga deposit. On the Kola Penin., in West Keivy Ridge, near Rovozero (Rov Lake) transparent quartz, enriched with needle-shaped plates of astrophyllite was found. In 1797, in the Middle Urals, to the north from Yekaterinburg, near Shaytanka a deposit of perelift was opened. That’s why this stone is called – Shaitan perelift, and after other discovery locations – Zotov perelift and Makarov perelift. In the Urals, smoky quartz with inclusions of bright green short-columnar crystals of epidote has received a name of ukropnik (“from fennel”). At gold-ore deposits of Transbaikalia and the Khabarovsk Region hydrothermal veins with stripped quartz aggregates the type of perelift is found. In Khakassia, at the Verkhne-Askizskoye deposit ornamental rhodusit, replaced with opal is extracted. In the Ukraine, among ornamental and collection varieties of quartz we should mention quartz crust with water-transparent crystals, from 0.5 to 15 mm. in size. Usually they are two-sided and have strong luster. They were named after the discovery location, for example – Marmarosch diamonds in the Carpathians Mts. and so on (See App. 13). In Romania, at the Cavnic deposit, (form. Kapnik) quartz crust is of rose-red color, because of admixture of rhodochrosite. In Namibia, at the Otie deposit, quartz with inclusions of aggregates of riebeckite with ochre because of its ornamental quality has received its own trade name – pietersite. In South Africa, in the northern part of the Cape Prov., in the Asbestos Mts., there are the largest deposits Priska and others with crocidolitic hawk’s-eye and tiger’s-eye. They take the territory of hundreds of square kilometers in the zone, from 5 to 50 km. wide, and has thickness of layers about 1 km. Country rocks in this zone are filled with fine veins of crocidolite from 1 to 5 cm. wide and more. Small deposits of tiger’s-eye are in India. In Western Australia the deposits Wittenoom Gorge and Yarra Creek are exploited, where tiger’s-eye and hawk’s–eye exist. In the U.S.A., near Atlanta, Georgia, prase is found; in Utah at the Bingham deposit – bing-hamite. In Arizona, ornamental variety of blue quartz with chrysocolla is extracted.
Ornamental rocks. Among magmatic rocks with quartz we can mention greenish quartz porphyry from Tibet with inclusions of aventurine quartz. This ornamental stone has its trade name – Tibetan quartz or eosite. In American gemology eosite is the name for ornamental quartzite of bluish-white color with brownish-red veins and spots, which contains inclusions of small pyrite crystals. In the U.S.A., in Texas, brownish granite with grains of blue quartz with chatoyancy is very popular. This ornamental rock has a trade name – llanite or llanoite. In metasomatic rocks quartz is the main element of lepidolite greisen and muscovite greisen, which are used sometimes as ornamental rocks. In Kazakhstan, an example of ornamental metasomatic rock is rodusit quartz, from the Karsakpaiskiy Dist., Pribalkhashia. There, in serpentinites of the Kenterlausskoye jadeite deposit in the Karaganda Region, unusual transparent light blue-gray icy quartz was found. It is represented with lenses, up to 40x8 m. in size; it is characterized with intensive gas-liquid and mineral inclusions. Similar icy quartz was found also in the Middle Urals – at the Beresovskiy gold mines; in East Transbaikalia – at the Adun Chilon deposit; in the southern part of the Krasnoyarsk Region – West Sayan Mts., among albitites in hyperbazite of the Borus jadeite deposit. In Russia, among metamorphic rocks, we can mention ferrous quartzite from the Olenegorskoye deposit, Kola Penin.; it is also found in Karelia – at the Kostomuksha deposit; in the Kursk Region – at the Lebedinskoye deposit; in the South Urals – at the Taratash deposit; in the Tyva Rep. – at the Mugorskoye deposit; in the Primorskiy Region – at the Ussuriskaya group of deposits. In Karelia an example of this type is raspberry quartzites of the Shoksha deposit, situated in the Shokshinskaya Bay of Onega Lake, to the southeast from the city Petrozavodsk. In the South Urals, in the Chelyabinsk Region, in the Taganai Mts., near Zlatoust, there are aventurine quartzites of this type; in the Karabash Dist. – figured quartzites of the Novo-Andreevskoye deposit; and in Bashkortostan, near Beloretsk, at the Kirel’skoye deposit with small content of aventurine variety – micaceous quartzites. In the Altai, such rocks are rose quartzites or belorechites of the Beloretskoye deposit on the Belaya River opened in 1807. In the Amur Territory, alunite quartzites of metasomatic origin were discovered at the Oktyabr’skoye deposit on the Zeya Rever; in Buryatia Rep. – it is rodingite quartzites of the Usutaiskoye deposit. In the Ukraine rose-red Ovrutch quartzites at Ovrutchskoye deposit are exploited, and at the Krivorozhskoye and Zheltorechenskoye deposits – ferrous quartzites. In Kazakhstan, near Kounrad (now Konyrat), dumortierite quartzites at the Ak-Shoky deposit are known. In South Kazakhstan, in the Jamboulskiy Region, there is the Makbel’skoye deposit of micaceous quartzites with admixture of blue kyanite and aventurescence. In Western Australia, in the region of Spargoville, there is a deposit of fine-grained quartzite of green color, which received a trade name prase. There is also the Wittenoom Gorge deposit in the Hamersley Range, where silicificated rock with hematite and crocidolitic tiger’s-eye (trade name tiger iron) is extracted. In sedimentary rocks quartz is a rock-forming mineral for diatomite, limnoquartzite, chert and sandstone. Ornamental varieties of limnoquartzites are extracted in Slovakia, at the deposits Bartošova Lehotka, Stará Kremniiãka, Banská and others. Copper sandstone as an ornamental stone in Israel is extracted on the Sinai Penin., in the region of Eilat from the ancient times. In Russia copper sandstone is known in the Krasnoyarsk Region, at the Pechischenskoye deposit; in Uzbekistan – at the Naukat deposit, near Qarshi. In the U.S.A., in California, solid diatomite of white or ivory color is extracted; it is used in stone carving.
Unique Crystals. The largest crystals of quartz were found in pegmatites. The largest milky-white crystal, about 50 m high with well-formed superior part, was found in Namibia, in the Damarland Mts. There were also other findings registered: less large crystals from 7 to 12 m. long. In 1938, in Brazil, in the region of Diamantina, Minas Gerais, a two-sided crystal of quartz was extracted, 5.5 ton. Another large crystal, 5.5 m, long and 40 ton, was found at the Longo Pit deposit t, in area Itapori, Goiás. In 1997, there was found another giant crystal of rock crystal, which was called “Monte Pascuala”. It was evaluated in $50,000. In pegmatites of Madagascar a crystal, 7 m, long, was described. In the Ukraine, in miarolitic pegmatites of the Vohlynskoye deposit, a unique in size and quality crystal of morione was extracted, 2.7 m. long and about 10 ton. In East Kazakhstan, in the Tarbagatai Ridge, at the Akzhailyau deposit, in a quarry a large quartz crystal was opened, 10 m. long and more than 70 ton; in pegmatites of the Kaibskiy Ridge, in Pribalkhashia, a crystal 13 m. long was found its length reached 3.5 m., its width in cross-section was 1.6 m. In 1959, in Central Kazakhstan, at the Kent deposit, from a miarolitic cavity in pegmatite they extracted a short-columnar crystal of quartz, more than 7 ton weight, 2.4 m. long, 1.15 m. wide. It possesses mosaic-block structure and clear color zones, from gray in the base to colorless in the center and from smoky to morione at the frontiers. Crystals of quartz, 3-5 ton weight, were found in pegmatites of Eastern Kazakhstan. Crystals less in size, 1-2 ton weight, were extracted not rarely at deposits of rock crystal at the Urals, Aldan and the Pamirs Mts. In the Museum Hist. Nat., Paris, in the collection of large crystals there is a smoky quartz 4.05 kg. In the Smiths. Inst., Wash., a quartz crystal from Namibia, 600 kg., is kept. In Geologi Inst. Komi scientific ceter, Syktyvkar, there is double terminated crystal quartz weigh 1350 kg. from Dodo deposit, Subpolar Urals Mts.
Synonyms. (See also App. 13): Rock crystal, from Gk. “crystallos” – ice, because of the similarity with ice – Mountain crystal | Crystallus, Old | Alanson diamond | Cubic diamond | Pseudodiamond | Simili diamond | Juga, anc. Russ., syn. juga stone | Gwindel, after the discovery location at Gwindel, Switzerland | Pangonion, by Agricola | Babylonian quartz, syn. Babbel quartz or Babel quartz | Quartz bird’s eye | Piezoelectric quartz | Steklez, Old Russ., from glass, because of its transparency | Glacial stone, obs. | Ice stone, Old. Russ. | Zepterquarz, Germ.
Smoky quartz – Cairngorm | Morione amethyst | Smasen’ crystal, local Urals, obs. | Scotch pebble | Brazilian quartz | Brown quartz | Scottish quartz | Rauchtopas | Smolyak, local Urals, obs., because of its dark smoky tone | Cairngorm (Caingorm) stone | Scottish stone | Struganez, local Urals, obs., because of it’s facets | Suslenik or Siberian suslik, Old Russ. | ~ topaz: orange ~, Pyrenees ~, rotten ~, saffronite ~, Scottish ~, smoky ~.
Morione, from Lat. “mormorion” – dirty, because of its color – Black quartz | Smasen’, local Urals, obs. Russ. | Smolyak, local Ural., obs. Russ. | Tumpas local Ural., obs. Russ.
Citrine, according its color, from Old French yellow – Cereite, from Lat. “cera” – wax, because of its color | Pontic chryselectrum, by Pliny the Elder | Golden citrine | Spanish citrine | Madeiracitrin | Melichrysos, obs. | ~ quartz: gold ~, golden ~, hyacinth ~, yellow ~. | Madeira stone | Bahia topaz | Madeira topaz.
Citrine, received with annealing – Topaz quartz and others (See App. 13) | Schafranite.
Green quartz. – Buddstone | Chalchihuitl, Mexican name | Chrysoquartz | Edinite | Gibsonville emerald | Emerald matrix | Olivine quartz, according its color | Perdine, violet | Peridine, green, annealed | Emerald plasma | Prase (prasem), from Gk. “prasios” – leek-green | Prasiolite (prasilite) | Chrysoprase quartz | Emerald quartz | Shramov quartz | Vermarin, obs.
Red-brown quartz – Apricotine, obs. | Brown ferrous chert | Compostella hyacinth, after the discovery location at the Santiago de Compostella deposit, Spain | Spanish hyacinth | Siliceous iron ore | Pandaura | Ferrous pebble | ~ quartz: bloody ~, polychromatic ~, red ~, strawberry ~. | Rubos | Ancona ruby | Compostella ruby | Sinople (sinopal, sinopel), obs.
Dark blue or light blue quartz – Moss crystal | Lazurquartz | Azure quartz | Sapphire quartz | Safirina, obs. | Siderite, Old | Sidnit, Germ.
Quartz hair stone – Binghamite, after the famous Amer. researcher W.D. Bingham | Chrysothrix, obs. | Crispite, after the discovery location near the Crispalt Mt. in the Alps | Actinolite quartz | Cacixenite quartz | Rutile quartz | Sagenitic quartz | Tourmaline quartz | Pietersite, after S. Piters from Namibia, who send this stone onto the trade | Sagenite, from Gk. “sagena” – net, because of grating joints of rutile needles | ~ stone: acicular ~, Amour’s ~, echinoid ~, hair ~, Amour’s hair ~, Thetis hair ~, after the name of the Gk. sea goddess Thétis, silky ~.
~ cat’s-eye: actinolite ~, amphibole ~, Bavarian ~, Harzian ~, Hungarian ~, occidental ~. | Griqualendite, after the Griqualend deposit, South Africa | Kathophtalm, Germ., obs. | Satin stone | Silky stone.
Aventurine quartz (See Aventurine) – Astrumit | Quartz aventurine | Leonite | Ferrous quartz.
Asterix – Quartz-asterié | Star quartz | Rose star quartz | Starolite.
Chatoyant quartz – Cotterite | Craquele, Fr. | Iris | Indian opal | Quartz opal | Craquele quartz | Iris quartz | Pearly quartz | Rainbow quartz | Scambia.
Quartz with native gold: – Gold matrix | Gold quartz | Golden quartz.
Veined quartz – Gangquarz, Germ. | Icy quartz, because of its similarity with ice | Marble quartz | Milky quartz | White quartz.
Perelift. ~ agate: breccia ~, perelift ~, quartz ~, shelly ~, Ural ~.
Ornamental rocks. – Conglomerate, from Lat. “conglomero” – I collect | Diatomite, after the content, syn.: – infusorian earth, kiselgur, from Germ. “kisel” – sandstone and “gur” – deposit. | Sioux Falls jasper, quartzite after the discovery location near Sioux Falls, South Dakota, the U.S.A. | Alunite quartzite | Aventurine quartzite | Beloretskiy quartzite, after the discovery location on the Belaya River, Altai; syn.: belorechit, Belaya River rose agate, Beloretskiy rose agate, Beloretskiy rose quartzite | Blue quartzite, after its color, which depends on dusty admixture of carboneous substance, magnetite or dumortierite; syn. blue quartz | Amphibole blue quartzite | Dumortierite quartzite, syn.: red jade | Epidote quartzite | Feldspar quartzite | Ferrous quartzite, syn.: jaspillite, tiger iron, magnetite quartzite | Graphite quartzite | Perlite quartzite, after its structure with black sphaerolites | Pyroxene quartzite | Rhodonite quartzite | Sillimanite quartzite | Shoksha quartzite, after the discovery location on the coast of the Shokshinskaya Bay of Onega Lake, nears the city of Petrozavodsk, Karelia, syn.: red porphyry, Shokshinskiy porphyry, Shokha porphyry, shochan. | Spotted quartzite, syn. leopardite, after its color | Taganai quartzite, after the discovery location in the Taganai Mt., South Urals; syn. taganaite | Tourmaline quartzite | Vesuvianite quartzite | Sandstone, after the content, syn: copper sandstone, Eilat stone (elath stone), after the discovery location near Eilat, Israel | Opalescent sandstone, because of opal cement | Picture sandstone, syn.: landscape sandstone and limnoquartzite.
Quality improvement. Quartz is improved often with different methods. One of the easiest methods is annealing to weaken or to change its color, or even to make it colorless. The color of smoky quartz is stable up to 225°C, under the temperature more than 450°C quartz becomes colorless. In crystals of morione and smoky quartz with yellowish and brownish tones, a type of cairngorm, quality improvement with the method of annealing gives citrine color. Ural’s miners baked crystals in bread with the same aim. The most part of citrine in the trade net is nothing else than annealed under the temperature up to 550°C smoky quartz or amethyst. It is colored more intensely than natural citrine; it has reddish tone and has no pleochroism. Difference in color of such annealed citrine led to a plenty of names for the product (See App. 12). That’s why CIBJO recommends a general term for these varieties – topaz quartz.
Another method of quality improvement of quartz is ionic implantation. So, implantation of iron with further annealing makes from rock crystal – yellow-orange citrine. One more method, the most ancient of all, to improve quartz is it’s annealing with further fast cooling. It leads to producing multiple cracks, which are filled with colors; for example, green – Indian emerald; red – pandaura or fiery quartz; and also blue – imitation of sapphire. Quartz, improved in such way, received trade name craquele quartz, from Fr. craquele – a net of fine cracks on the glaze surface of china, which gives a decorative effect. Such cracks on quartz can appear in natural conditions, too. Modern methods of changing color of quartz are also: X-rays or gamma rays irradiation with isotope cobalt-60 to receive smoky quartz, citrine and prasiolite. Recently, the method of quality improvement was invented: covering the surface of crystals with fine metal films. Gold films lead to iridescence from golden-blue to light blue – aqua aura quartz. Another type of films produces amethyst color.
Cut Gems. Even the ancient human beings knew quartz and its varieties. Simple adornments and amulets were made from this solid and beautiful material, easy in processing. Transparent crystals and nice pebbles are found in ancient tombs and living places. In Ancient Egypt, rock crystal played a big role in the cult of dead ones. An image of a dead person should be cut on it; it became a place of location of his or her soul. During the excavations in Ancient Babylon the first quartz lenses were found, which had been produced 6 thousand years ago. In the tomb of Tutankhamen (14th cent. B.C.) sunglasses from morione were found. In an ancient Greek tomb near Mycenas, of the 6th cent. B.C., a flat vase from rock crystal in the shape of a bird was found. With the flourishing of glyptic, ancient masters have learnt to use all the varieties of quartz. A sample of using of rock crystal is a gem, 5.1x3.8 cm., with a portrait of Lucius Ver (Italy, 2nd cent. A.D.) in the collection of the State Hermitage, SPb. In Ancient Greece, smoky quartz was used in gems, stamps, and beads from the earliest times – 334-30 B.C. Objects from it were also popular in Ancient Rome. The Emperor Nero had two bowls cut out from the rock crystal. At the same time, from this material a perfect urn was made, 27 cm. height, 30 cm. breadth, kept among the national treasures of France now. From the deep antiquity “magical” balls from quartz crystals were highly valued. Such a ball with a “flower” inside it was propriety of G. Agricola. In Byzantium, such a ball was a symbol of the emperor’s authority. It became a source of the “globe” – one of the State regalia of Russian Tsars. In the medieval Europe small rock crystal balls, such as victory-stone, were hanged at military standards and weapon. The biggest, ideally transparent rock crystal ball, 48.62 kg., is kept in the Smiths. Inst., Wash. It was cut out in China from a crystal more than 450 kg., which had been extracted in Myanmar (Burma). The bigger ball (now it is lost), 75 cm. in diameter, was cut out in Japan, also from a rock crystal from Myanmar (Burma).
At the East images of Buddha were cut out from crystals of quartz. In China, eye-glasses from rock crystal have been known since the 5th cent. B.C. Examples of adornment from quartz, dated to the 1-3ss cent. A.D., are amulets in the shape of a hare, a duck and a fish in the collection of the State Hermitage, SPb. Many unique objects by ancient jewelers and stonecutters were made from this noble material. A unique masterpiece of the epoch of the Sasanides (6th cent.) is the “Khosrov Cup” from rock crystal, framed with gold. Its cross-section is 28 cm.; a portrait of Khosrov is engraved on the central disc. The famous “Skull of Death” of Maya priests in the Museum of American Indians, an American archaeologist F. Mitchell-Hurgess found, during the excavations of the Maya city Lubaantuna in the jungles of Honduras in 1927. It is cut out from a whole of rock crystal and has a weight of 5.2 kg. Later, in Mexico another skull of Aztecs was found, bigger in size – 21 cm. in cross-section, 15 kg.
An art of stone-cut on quartz reached the highest point of its development in the epoch of the Renaissance when gems, stamps, animal figures, bowls, bottles and other things were cut out from its crystals; often they were framed with noble metals. In the 17th cent., they mounted faceted rock crystal in lead. In the Grün. Gew., Dresden there are unique bowls from rock crystal of French work, 17 and 24 cm. height. In the Kunst. Hist. Museum, Vienna the “Crystal Flute” is kept – a gift by Napoleon Bonaparte to a young flutist L. Druhe. In the Armory Museum Kreml., Moscow there is a large collection of Wessels from rock crystal, including the “Crystal Samovar of Peter the Great”, which was made from one crystal. Significant quantities of unique items from rock crystal are exhibited in the State Hermitage, SPb. There is a medieval lamp of an antique shape, richly decorated with gold and enamel; a wine cask in gold hoops, decorated with cut gemstones; a vessel in the shape of a lying dragon, 65 cm. long; jugs and bowls of European work of the 17-18ss cent. Besides, there are two vases from Altai Mts. tourmaline milky quartz, 60 cm. height, made at the Yekaterinburg lapidary factory (1803), and many small items, such as snuff-boxes, bottles, including produce of Chinese work from quartz hair stone. At the times of Catherine the Great, things from quartz with mineral inclusions were popular, for instance amethyst with goethite from the Volk-Is. and rock crystal with inclusions of rutile – quartz hair stone.
Rock crystal was used perfectly by French jeweler Louis Cartier in his magical clocks. Russian jeweler K. Fabergé used quartz as a material for the souvenir Easter Eggs, including model of the monument to the Emperor Alexander III (1910) and in the “Winter Egg” (1913). The last one was sold at the auction in 2002; it was evaluated in $6 million. The biggest work of art from carve rock crystal is a transparent screen “Discovery of Moses”, 150x175 cm. in size, in the Nat. Hist. Museum, Chicago. There is also kept a Venetian case from engraved rock crystal, 125x175 mm. in size. The most popular faceting for rock crystal is a brilliant one, as well as a combined one. The biggest faceted stone 19,548 ct. is 25.5x14.1x10 cm. in size, earlier the biggest stone had 7,000 ct., and it was in the collection of the Smiths. Inst., Wash. It was faceted from a rock crystal, extracted in Brazil. In the same museum, there is a stone 625 ct., from a crystal of quartz, extracted in New Hampshire, the U.S.A. It is name “Bahia”, a 5-foot, 448 pound carving rutile quartz sculpture created by Amer. lapidary artists from California over the course of seven and a half years. It is on display at the Nat. Hist. Museum, Los Angeles. Small crystals of quartz with strong luster, like Marmarosch diamonds, are used in jewelry without processing. From the 19th cent., because of the development of the production of crystal glass, using of rock crystal in jewelry is decreasing. Smoky quartz, as like as rock crystal, is used in a cut shape as engraved insets and stone carving. In the State Hermitage, SPb. there is a vase from smoky quartz, 42 cm. height, made at the Peterhof lapidary factory (about 1800); it has holders in the shape of female figures from gilded silver. The biggest of cut stones has 8,580 ct.; it is kept in the GIA. In the Smiths. Inst., Wash., the biggest pieces of smoky quartz has weight 4,500 and 1,695 ct. There is also an egg, 900 ct., at the same collection, which was cut from a crystal of smoky quartz; and faceted Brazilian citrines: 1,180; 783, 278, 265 and 217 ct. In the “magical clocks” by the firm Cartier the central part with hands usually is made from large blocks of transparent quartz. Such a clock “Mystery of Cartier” with citrine, 2.9 kg. and 230 brilliants were evaluated in $740,000 in 1995. Interesting examples of usage of cut quartz in the monumental art were realized in the U.S.S.R. In 1935, in the process of establishing of ruby stars at the towers of the Moscow Kremlin, an emblem “Hammer and Sickle” was made on four stars 2 m. wide, with incrustation from faceted rock crystal. On two other stars they made rays, coming out of the center of a star. It took 7,000 faceted stones from 20 to 200 ct. each, mainly it was rock crystal. In 1936, in the process of work over the mosaic “Map of the U.S.S.R.” 3,685 faceted stones, including 515 pieces of quartz were used. Oil-pipe-lines and centers of the oil industry were presented with smoky quartz; centers of production of construction materials were presented with citrine.
In the U.S.A., at the exhibition in Tucson (1997) a ball from tiger’s-eye, 50 cm. in diameter, was exhibited. It was made in Western Australia and has been evaluated in $12,000. Produce from Brazilian quartz hair stone with inclusions of large crystals of golden rutile won a great popularity among jewelers. As a rule, they are cut as cabochons and brooches. A large block of prase, 84.5x44.5 cm. in size, Princess E.R. Dashkova has brought from Italy to Russia. It was separated into two ovals, from which two tables have been made; they were gifted to the emperor Alexander I. Later, they were sending to the Armory Museum Kreml., Moscow. Since the 18th cent., masters of glyptic from the Urals have been using perelift to create artistic gems. This stone was used for a panahagia with an image of the prophet Daniel, some icons and other work of art. Modern jewelers from the Urals keep these traditions. In 1979, at the exhibition in Tumen a vase “Lake” from Shaitan perelift was exhibited. In France, in Paris the sarcophagus for Napoleon in the Cathedral of the House of Invalid’s has been made from raspberry quartzite. Quartzite for this sarcophagus, in the quantity of 27 blocks (the largest was 4.6x2.2x1.1 m. in size, 27 ton weight), was gifted to France by the Russian Emperor Nicolas I in 1847. K. Fabergé often used Beloretskiy quartzite in his stone-cutting work of art. In the State Hermitage, SPb. there is a vase from Pustynnikovskiy quartzite from the Belaya River, Altai Mts. Nowadays, this material is used successfully by another master of small stone carving, e.g. V.V. Konovalenko (1929-1989). Warm color of this rock is the best for parts of human bodies in small sculptures. In the work of art by the firm of K. Fabergé sandstone was also used, for example in a figure of a rhinoceros.
Legends. Rock crystal serves as a symbol of modesty and purity of thoughts for many peoples. It is an amulet for those, who were born in April, and a lucky stone for persons, who were born under the sign of Virgo. As a talisman it gives insurance in business contacts. It is supposed, that rock crystal could be a universal transmitter of thoughts and could help in telepathic communication. It also helps to avoid nightmares. Rock crystal is regard as a national symbol of such countries as Switzerland, Belgium and Japan. In the U.S.A., geode quartz – a symbol of the Iowa State. Smoky quartz as a talisman awakes fantasy. It is a stone of dreamers and drug-addicts. There is an opinion, that it is healing drug-addicts. Astrologers treat smoky quartz as a lucky stone for those, who were born under the sign of Libra. This gemstone is regard as a national symbol of Scotland. Citrine is a stone, which is linked with gambles; it is a stone of swindlers, brokers and people, who work with hands and head both. As a talisman, it helps to correct defects of pronunciation and to express thoughts, that’s why in Ancient Rome it was known as speaker stone. Astrologers treat citrine as a lucky stone for those, who were born under the sign of Gemini and Aquarius. Eyes quartz has properties of protecting amulets. It is supposed, that cat’s-eye protects in love, tiger’s-eye – in business activity, hawk’s eye – in the fighting against enemies. Astrologers believe, that tiger’s-eye is a lucky stone for those, who were born under the sigh of Gemini, hawk’s-eye – Aquarius, and cat’s-eye – Capricorn.
Synthesis. Synthetic quartz in industrial scale is received with the hydrothermal method. As jewelry rough material its transparent varieties are used: colorless – synthetic rock crystal, yellow – synthetic citrine, orange-brown, brown, violet – synthetic amethyst, light blue – synthetic blue quartz and dark blue – synthetic perunite quartz or synthetic Siberian blue quartz, green – synthetic Siberian green quartz or skrasiolite; as well as multicolored: violet and yellow – synthetic ametrine, green and rose – andalusite and synthetic rosa quartz with admixture of phosphorus. Besides, milky-white opalescent variety is produced – synthetic opal-like quartz or synthetic opalescent quartz. In the U.S.A., at the exhibition in Tucson (1997) synthetic quartz crusts with small crystals covered with bluish-lilac film of titanium, were represented under the trade name titanium quartz.
Similar Gemstones & Imitations. Quartz looks like topaz, nepheline and phenakite. From topaz it differs with less hardness and density, absence of joints; from phenakite – with its optic effects. For nepheline greasy luster and less hardness are typical. Many yellow gemstones can be treated falsely as citrine, the biggest similarity with it such stones have: Adularia from Madagascar, beryl and topaz. The main imitation of rock crystal is glass with high refraction, known under names: strass, Rhine pebble, Bohemian crystal or just crystal, as well as synthetic quartz and quartz glass. Glass imitations with different inclusions are popular, including those with metal dendrites or inlayed colored foil – smaisen’. Synthetic cat’s-eye, fibrous-eye or Chinese eye – it is an optic-fibrous material – borosilicate glass up to 15 colors. Another imitation is catseyte, which looks like chrysoberyl cat’s-eye of the highest quality. It is received on the base of fibrous rare-metal silicate, melted in the complete mass with saving of parallel orientation of fibers. In France, such imitation is called also in trade – Lyon’s-eye. The most widespread imitation of citrine is yellow glass, sometimes – synthetic citrine or yellow synthetic corundum.
Amethyst (Amethyst—Améthyste—Аметист) (Theophrastus, 315 B.C.), from Gk. amethystus, and from Lat. amethystos, “not drunken” because the stone was believed to prevent intoxication. It is known from the ancient times by Pers. and Arabic – jamast, banavash – violet; Armenians – megasik; Hebrew – kerkchan or achlamach, from “chalam” – dream, because it is supposed to send night dreams.
Composition & Properties, deposits. – (See quartz). Amethyst is a violet variety of quartz. Here also its variety is described – rosa quartz. In quartz veins and mineralized joints amethyst are found mainly as short-columnar crystals with dominating development of rhomboid facets and as scepter amethyst. Scepter excrescences of amethyst can be observed both on rock crystal and on smoky quartz or citrine. The size of amethyst crystals is usually not more than 10-15 cm., but sometimes they reach even 45 cm. However, large crystals are dimmed as a rule. Color amethyst depends on the structural admixture of iron (Fe3+). Its tones and specifics of color dispersion in crystals from different deposits differ obviously. The most evaluated are thick purple colored Siberian amethyst, then – moderate bright Uruguay amethyst and pale Brazilian amethyst. On Madagascar amethyst is of lavender-blue tone, and in Brazil and Uruguay its color is brownish-red and often not even. Dichroism from reddish-violet to bluish-violet is not rare. Dispersion of color in amethyst crystals is zonal-sector one; and it is connected with sectors of growing of facets of big rhombohedron. In pyramids of facets’ growing in a prism crystals are colorless or dimmed. Character of coloring is more complicated in twin crystals. Sometimes there is abnormal stripped coloring like tiger skin. Zones of amethyst color alternate with dimmed or colorless ones are not rare. Separate varieties are ametrine and prasiolite. In ametrine alternation of sectors of amethyst and citrine color is observed, and it should be stressed that amethyst color is connected with a sector of facets’ growing of big rhombohedron, and citrine color – with small rhombohedron. Green prasiolite is received usually with annealing of amethyst, but rarely its natural varieties are found. In amethyst veined quartz or violet quartz color is usually even.
Amethyst crystals often contain multiple inclusions of different minerals. The most common of them are: goethite, hematite and rutile. Amethyst with inclusions of goethite needles was called onegit, after the discovery location on the Volk-Ostrov (Volk-Is.) in the Onega Bay of the White Sea. Inclusions of separate needles of these minerals product also amethyst hair stone, and such crystals with fine flakes of hematite are called mosquito amethyst. In aventurine amethyst plates of hematite are disposed in parallel to the facets of rhombohedrons and lead to effect aventurescence. Because they are absent near the edges of the upper part of a crystal, after perpendicular cutting of such crystal a false effect of star quartz appears. Such amethysts from Mexico, the Sonora State, are called strawberry quartz. In Brazil, in amethyst hair stone along with rutile there are inclusions of needles of cacoxenite —cacoxenite quartz. In Uruguay, at the Artigas deposit, at the facets of amethyst rhombohedron opalescence like in adularia was observed, which was called the Lowell effect, after the surname of D. Lowell, who discovered it. In Kazakhstan, at the iron-ore accumulations of the Mangyshlak Penin., amethyst crusts are found, which are represented with crust aggregates of amethyst crystals with zonal coloring. The size of these crystals is not more than 5-7 cm., and their outer zones, enriched with inclusions of goethite, are colored in brownish-yellow, dark red and brown tones. Appearance of citrine color in amethyst zones usually is applied with inclusions of goethite and hematite. Plates of hematite, depending on their quantity and size, can lead to red or black color. In the outer zones of red crystals sometimes there are threat-like inclusions of pyrite, which give silver tone and make color of crystals more light. Multicolored quartz crystals of Mangyshlak perform a plenty of jewelry rough material.
Deposits. Forming of amethyst is connected with the finishing part of hydrothermal process in pegmatites, ore, crystal-containing veins and chalcedony almonds. There are metamorphosed veins, formed with columnar aggregates of amethyst quartz, which separate parts perform crystals of zonal structure with alternation of milky-white and amethyst zones, so called chevron amethyst. Another type of deposits is a zone of cracks with amethyst crusts. In Russia, one of the first amethyst deposits was the Volk-Ostrov (Wolf Is.) in the White Sea, where its crystals are in the zones rock jointing in diabases and shungite slates. Geodes with amethyst were not more than 10 cm. in cross-section, and the size of crystals was not more than 2-3 cm. Amethyst was characterized with pale color and rich inclusions of goethite. The second most ancient deposit of amethyst on the Kola Penin. was Mys (cape) Korabl’, 200 km. to the southeast from Kandalaksha, on the Terskiy Shore of the White Sea. In 1680-1790, there the first mine-works were held by monks of the Solovetskiy cloister. There, in quartzite sandstone, seven stock works with mineralized fissures were found; their walls were encrusted with crusts of small amethyst crystals. The square space of crusts reaches 20 cm.2, the longest crystals are up to 1 cm. Their color is even, pale violet to bright violet, sometimes with velvet black tone. In the places of intensive crushing rock splinters, covered with crusts, perform amethyst breccia. Amethyst crusts are used for jewelries. Nowadays, the Terskiy Shore deposit is classified as a natural object of geological interest. Because of this more perspective are deposits of amethyst crusts a bit far from the seashore – near Kitskoye Lake. In the Middle Urals, the first mentions of findings of amethyst is dated with 1668. In the 18-19ss cent., amethyst deposits Murzinka, Mokrusha, Vatikha, Tal’yan and Adui mines were found there in pegmatites, as well as smaller ones. They are connected with quartz veins and pegmatites of the Murzinsko-Aduiskaya gemstone field. The sizes of amethyst crystals are usually not more than 10-12 cm. long there. Their color is from light to bright violet with obvious zones. The output of material for cutting from the extracted amethysts was 3-4%. The most precious velvety amethyst, or Siberian amethyst, was found there. In the South Urals the Itkul’skoye deposit in the northern part of the Chelyabinsk Region was found, as well as some other isolation with rough material of rather low quality. On the western slope of the Subpolar Urals Mts., in the upper reaches of the Kozhim River, the amethyst Khasavarka deposit in 1944 was found and studied in 1970-s. This deposit is characterized with scepter-shaped amethyst crystals growing on rock crystal. Crystals are short-columnar, their size is not more than 10 cm. Their color is from pale to dark violet, zonal-sectorial one. The balance resources of rough materials of this deposit are generally valued. In East Siberia, in the Krasnoyarsk Region, amethysts are found in almond-stone basalts; they are characterized with small size of crystals (not more than 5 cm.) and low quality of rough material. In the Irkutsk Region, large geodes with amethyst are found at the iron-ore Angaro-Ilimsk deposits in the middle reaches of the Angara River. The size of pale violet crystals is not more than 5 cm. long. At the Kopaevskoye deposit of the Katskaya group there is a stalactite forming up to 20 cm. long with chalcedony nucleus, which is covered with radial aggregates of crystals of transparent quartz with amethyst headers. In the East Sayan Mts., there are the Gorelovskoye and Maloknyshinskoye amethyst deposits; in 1969-1973 the Obman deposit in the southern part of Yakutia was exploited. In 1970-s, in the Magadan Region, in the upper reaches of the Kedon River, the Omolon River tributary, the Kedon deposit was being studied – in effusive with collection druses of reddish-violet amethyst up to 5 cm. long, and sometimes up to 10 cm. long. In the upper reaches of the Kolyma River, on the Ol’skoe Plateau and at the Agatovskoye deposit, amethyst is connected with hydrothermal veins in effusive rocks. In the Khabarovsk Region, on the left bank of the Amur River and in its low reaches, to the north from Chlya Lake, there is the amethyst deposit in the Tropinova Mt. Amethyst is found in nests in pegmatites veins, sometimes together with aquamarine. In the Primorskiy Region gem-quality amethyst is known in ore veins of the Dal’negorskoye deposit. In the north-western part of the Kamchatka Penin. amethyst exists at the Palanskoye deposit in almond-stone lava, near Palana.
In the Caucasus, the most part of amethysts are placed at agate deposits in effusive layers. Exclusion is the Dashkesan deposit in Azerbaijan, where amethyst in crystals up to 30 cm. long fills caves in skarns. However, the output of gem-quality rough material there is rather low. In Central Kazakhstan, at the pegmatites deposit Kent, veined amethyst quartz was extracted. In the north-eastern part of the country, in the Kustanai Region (now Kostanai), at the iron-ore Sokolovskoye deposit there are caves encrusted with amethyst crystals. In South Kazakhstan, to the north from Alma-Ata, near Saryozek, there is the Arkharly deposit with parts of breccia veins of amethyst quartz. The length of these veins is up to 1 km., the thickness is up to 2-3 m. besides, and there are amethysts in effusive rocks. In Uzbekistan, in the Pskem Ridge, in quartz veins among skarns there is the Miskansay amethyst deposit with crystals up to 20 cm. long. In the Maidan-Tal Ridge, there is the Shamterskoye amethyst deposit in pegmatites and in quartz veins. In the Kuraminskiy Ridge, in effusive there is the Kumkol deposit with phantom amethyst color of rock crystal, up to 7 cm. long. In Kyrgyzstan, in the Djanghijalskiy Dist. of the Osh Region, there is the quartz veins’ field Kuru-Uchkurt, where nests with amethyst crystals up to 8 cm. long were found. In Northern Tadzhikistan, in the Karamazor Ridge, there is the Kandzhol deposit, where amethyst cements breccia in a giant vein, 10 km. long. Amethyst breccia with the thickness up to 8 m. has been a popular ornamental stone since the Middle Ages. In the Hissar Mts., 45 km. to the west from Dushanbe (Dyushambe), the Selbur amethyst deposit in andesites was found. Quartz veins are formed with parallel-columnar aggregate of quartz and amethyst of violet color in the central part of veins. This amethyst is good only for the processing with the method of tumbling. In the Karateginskiy Ridge, the south spur of Hissar Mts., 135 km. to the east from Dushanbe, there is the Kalotskoye (Sarimazarskoye) deposit of amethyst. In the West Pamirs Mts., in the Vanch Dist., amethyst was found in rock crystal-containing veins of the Rakzou deposit. In Mongolia, the amethyst deposits Kharnastu-Obo and Artz-Boga-Ool are connected with quartz veins and almonds in effusive rocks.
In Bulgaria, in the East Rodopy, at the hydrothermalore Mazharovo deposit ornamental amethyst is found. It is represented with breccia chalcedony-amethyst veins and radial aggregates in the shape of amethyst roses, which consist of crystals, not more than 1 cm. each. To seal bands of these veins parallel-columnar aggregates of non-transparent amethyst, from 0.3 to 1 m. thick, and slit-shaped caves with amethyst crusts are linked. In Romania, amethyst is extracted as an additional material at the ore deposits Porcuria, Cavnic (form. Cavnic), Baia Mare, Rosia Montane and Sekerymb. In Poland, there are several amethyst deposits in Lower Silesia. In Slovakia, amethyst was extracted from ore veins of the Banská ·tiavnica deposit. In France, on the deposit Auvergne dark-violet crystals Auvergne amethyste were extracted. In Germany, amethyst is known at the agate deposits near Idar-Oberstein, Rhineland-Palatinate. In Great Britain, beautiful amethysts were found on the Sark Is., Norman Iss. This amethyst has also a local name – Sark’s chert. Amethyst was also extracted in Norway, and Finland. In Finland, at the Pelkosenniemi deposit in Central Lapland, an amethyst crystal of 650 kg. was found.
In Africa, amethyst deposits are known in Tanzania and also in Namibia – Platveld and Cape Fria. In the 20th cent., after the discovery of a group of deposits of amethyst in the South Prov. of Zambia this country became the largest supplier of this stone to the world market. Amethyst in crystals up to 30 cm. long is extracted at the deposits Kalomo, Kerl’yu, Simamba, Mvacambiko, Mindiko, Siamani and Namazambwe. Besides, on the Zambezi River rich amethyst placers are exploited. At the neighboring territories, in Zimbabwe, to the east from Kariba Lake, there is also the amethyst similar Mvacambiko deposit. In Morocco, amethyst deposits are in the Lofty Atlas Mts., to the southeast from Marrakech, near the pass Tizi-n-Tichka. On Madagascar, to the west from Fianarantoza, the deposit of amethyst was found with scepter-shaped crystals up to 20-60 cm. long, up to 60 kg. In the same region, two-sided scepter-shaped crystals were also found, up to 10 cm. long. At the Mangatobangy deposit, to the west from the Ambositra, amethyst is represented with scepter-shaped excrescences on quartz, 30x10 cm. in size. Beautiful dark violet amethysts are extracted in pegmatites near Ambatomanga, and Tongafeno. In Australia, amethyst deposits are situated along the eastern coast in Queensland, New South Wales and Victoria States, and on the Tasmania Is. The best amethyst is extracted in New South Wales, at the Glen Elgin deposit, New England Range, and deposit near at the Tingha. Since 1982, amethyst has been being extracted on the western coast at the Mt. Phillips deposit, to the southeast from Onslow. There are large amethyst crystals up to 5 kg. in this region. On the Northern Territory, small deposits of amethyst are situated to the southwest from Alice Springs. In South-East Asia, we should mention amethyst placers in India, on the Deccan Plateau. In the Madhya Pradesh State, amethyst is found in quartz veins near Shivpurï, and in the river valleys in the region of Jabalpur, and near Jaipur, Rajasthan. On Sri Lanka, it is extracted at the placers together with other gemstones. In China, amethyst deposits are located in the Shanxi Prov., in Korea – at the Onian mine, in Myanmar – at the deposit in the upper reaches of the Chindwin River, near Mainkuan. In Japan, amethyst deposits are in the Miyagi Pref., Niigata Pref., and Tottori Pref..
In Uruguay and Brazil there are the largest hydrothermal deposits in trap coverings with big geodes, filled with amethyst crystals and agate (See chalcedony). In 1900, in Brazil, near the Uruguay border, in the Rio Grande do Sul State the Ametistas deposit was discovered. The first geodes of amethyst, general weight 15 ton, which were extracted there, were brought to Germany and successfully exhibited in Dusseldorf in 1902. There are several amethyst deposits of industrial value in this state. At the Sierra do Mar deposit the size of the largest geode of amethyst reached 10x5x2 m., and its weight was 70 tons. Druses of amethyst from this geode, with crystals up to 10-15 cm. long – serratopas (Germ.), exhibited many museums of the world now. At the deposits in the Soledade Dist., in amethyst geodes there is quartz stalactite like forms, encrusted with crystals of amethyst. Perpendicular cuts of such “stalactites”, up to 15 cm. in diameter, are called amethyst flowers or amethyst rose. In the Pará State, on the right bank of the Araguaya River, in the weathering crusts there are Pau d’Arco large deposit near Marabá with amethyst crystals up to 50 cm. long. In the Espírito Santo State, at Mimoso do Sul deposit scepter amethysts are typical. In Minas Gerais State the largest crystal of scepter quartz, to 100 cm. long, was found. Annealing of pale colored rough amethysts from Brazil often gives citrine of high quality. In the Bahia State, in the region of Vitória da Conquista, amethyst deposits were worked out in quartz veins. The biggest amethyst crystals, up to 20 cm. long, were extracted at the Montezuma mine. After annealing this amethyst receives green color; it is known under the trade name peridine. There is also an ornamental variety – amethyst breccia, cemented with red chalcedony. Another deposit in this state is Coruia, where splinters of amethyst, 20x10x10 cm. in size, are used as rough material for facet and for stone carving. After annealing these amethysts receive yellow and orange-brown color; they are known under the trade name Bahia topaz. They’re also milky-white with brownish-red and half-transparent quartz with inclusions of hematite along the zones of growing in scepter-shaped headers of crystals is extracted. At the Joanina deposit, in caves of chalcedony-quartz vein in gneisses there are amethyst crystals up to 10 cm. long. Headers of crystals can be colored green or violet. Their color doesn’t change after annealing. In Uruguay, the most significant amethyst deposits are located in the Artigas Dept. – Catalan Grande; Paysandú Dept., Salto Dept., and Tacuarembó Dept. In Mexico, perfect amethyst crystals up to 20 cm. long are found at the Amatitlan deposit, Guerrero State. In the Veracruz State, in the region of Las Vigas, at the Piedras Parado deposit, in andesites, the size of scepter-shaped and two-headed amethyst crystals in geodes reached 10 cm. In the Guanajato State, amethyst is growing over stalactites up to 16 cm. in diameter, forming amethyst roses in perpendicular cutters. In 1964, in the southern part of Bolivia, the deposit of ametrine and amethyst Anahi, Santa Cruz Dept., was discovered. Ametrine is high quality jewelry material with sectors of amethyst and citrine color; its local name is trystine. At the mines Gaiba, Los Pobres and La Esperanza, Santa Cruz Dept., in limestones the best amethyst is extracted, sometimes together with rock crystal and citrine. In the U.S.A., mainly in the eastern states, there are small hydrothermal deposits of amethyst with crystals up to 45 cm. long. In the west, in Washington, the Denny Mt. deposit, King Co., is known; in Montana, Jefferson Co., in pegmatites – the Tall Mt. deposit; in Arizona – the Four Peaks deposit; and in Rhode Island State, near Ashawei. In the Colorado State, amethysts were found in effusive rocks at the La Garrita deposit and in the region of Creed. In New Mexico, the Vera Cruz deposit, near Las Vegas, was exploited. In Canada, in the Ontario Prov., on the northwestern bank of Superior Lake there is the large amethyst Thunder Bay deposit, which was exploited through many mines. The size of amethyst crystals reached there 25 cm. in cross-section; besides, amethyst crusts were extracted there as ornamental material, as well as country rocks with thick net of amethyst veins.
Synonyms. Purple agate | Amephusaky, obs. Russ. | Amephyst, obs. Russ. | ~ amethyst: Auvergne ~, aventurine ~, Bahia ~, blood ~, Brazilian ~, chevron ~, Madagascar ~, occidenbtal ~, oriental ~, polychromic ~, Russian ~, Spanish ~, tip ~, Ural ~, Uruguay ~, Vera Cruz ~. | Amethystine | Amethystizon, obs. | Amethystos | Amethystus, obs. | Bacchusstein | Latin diamond | Rock flower | Rose de France, Fr. | Hyacinth, by Agricola | Jamast, obs.| Lavendine, obs. | Violet quartz | Orchid stone, after its color | Sark stone, after the discovery location on the Sark Is. in the English Channel | Taljashka (taljanchik), local, Ural., after the deposit in the Tal’yan Mt., which was exploited by Ital. masters | Bahia topaz, from the Serra Salto deposit, Bahia State, Brazil.
Burnt amethyst – Brazilian amethyst | White amethyst | Peridine | Gold quartz | Saffronite |~ topaz: Madeira ~, noble ~, Salamanca ~, white ~, yellow ~. | Vermarin | Wareg, Old Russ.| Warenik, Old Russ.
Ametrine – Citrine amethyst | Gold amethyst | Lavendine (lavendrine).
Quality improvement. In the sunlight amethyst color is not stable, it is getting paler to colorless. After annealing under the temperature up to 200°C its color can disappear, but later it is restoring. After annealing less than 400°C the color is restoring only with gamma-irradiation. As a result of annealing of transparent amethyst under 500°C citrine is received, which is called gold quartz or burnt amethyst. The most part of gem-quality citrines is received with this method; they have more bright color with reddish tone. After annealing under the temperature more than 600°C amethyst becomes milky-dimmed and opalescent; it can be used as an imitation of moonstone. Transparent amethyst from Bolivia and from the Montezuma deposit in Brazil receives green color after annealing under the temperature 510°C. It non-transparent variety under the temperature 650°C becomes milky-green with white zones. There is also transparent green quartz – prasiolite, which is a naturally annealed amethyst. Its green color disappears after heating to 500°C, and after gamma-irradiation it is restoring sometimes (See quartz).
Cut Gems. Amethyst is the most precious gem in the group of quartz. It has been used since the deepest human history. In the East, beads, amulets and bottles for expensive aroma oils were cut from it. Amethyst beads, which were found on the Crete Is., were dated to the middle of the 3d millennium B.C. In the collection of the State Hermitage, SPb. there are several amulets from amethyst in the shape of frogs, dated to the 1-3ss cent. A.D. The first written mention of amethyst is in the work “On Stones” by Tirtamos from Erez, a student of Aristoteles (384-322 B.C.). In Ancient Greece and Rome, amethyst was highly evaluated; among the other varieties of quartz it was used in glyptic. One of the masterpieces by antique artists is “Bust of Mithradates VI Eupator” (132-63 B.C.), the King of Pontus; it is 3.1 cm. high, cut from transparent amethyst (1st cent. B.C.). Another bust from amethyst performs the Roman Emperor Trayan (53-117); it was taken by Napoleon from the treasury of the Prussian Kings to France. Another bust of an unknown Roman citizen, made from amethyst, 4.2 cm. high, is kept in the collection of the State Hermitage, SPb. There are also cameos on amethyst exhibited: “Portrait of Vespasian”, 1st cent. A.D., 1.8x1.2 cm.; “Bust of Victory”, Rome, 1st cent. B.C., 2.5x1.8 cm.; “Portrait of Ptolemy II”, Alexandria, 3rd cent. B.C., 1.8x1.5 cm. and others. In different museums there are four cameos on amethyst by the famous Roman master Dioscorid. There are portraits of the Roman Emperor Augustus (63 B.C.-14 A.D.), and his son, of Gk. ruler Solon (about 638-559 B.C.) and of Macenas. Amethyst was among the twelve gemstones at the breast-plate of the Judaist high priest in the Bible. In the Middle Ages, it was a favorite stone in monasteries and royal palaces. It was used for the decoration of altarpieces and church vessels.
In the epoch of the Renaissance, amethyst was treated as a symbol of modesty, humility and love to the God. According one legend, amethyst was in the wedding ring of Maria, Mother of the God. People, who had given some vows, and priests, were wearing it. That’s why it was called Bishop’s stone, vicarial stone and hierarch stone. Amethyst can be observed in the ring of the Pope and in rings, which he gives to cardinals in the process of their consecration. Before the 16th cent., in Russia, amethyst was evaluated higher than ruby; it was used in the decoration of crowns of the first tsars, crosses, icons and clothes of church authorities. After the discovery of amethyst deposits at the Urals and on the Volk-Ostrov (Wolf Is.) in the White Sea, it became better. After the discovery of the richest deposits of amethyst in Brazil and Uruguay in 1867, 10 ton of amethyst were brought to Europe at once, and its market price has fallen. Amanufacturer from the Urals, P.A. Demidov gifted to Catherine the Great a perfect crystal of amethyst with her carved portrait. The size of the stone was 7 cm. long and 5 cm. broad. In the collection of the Russian Empress Maria Feodorovna was a perfect amethyst with a carved portrait of the Emperor Alexander I. In the Museum-apartment of A.S. Pushkin in St Petersburg there is a walking stick of the poet with a knob from amethyst. The best amethyst in the world, in the shape of a big ball, decorates one of the State regalia of the United Kingdom – the scepter. From a crystal, which was extracted in Brazil, the biggest faceted amethyst was made, 1,362 ct. Other examples of faceted amethyst: 234.9 ct. and 43.2x35 mm. from Uruguay; and 361.5 ct. and 519 mm. in diameter from Brazil. In the Smiths. Inst., Wash. two amethysts from Russia are exhibited – a hexagonal cut stone in 90 ct., and a round cut one in 75 ct. In the British Museum, London there is cut amethysts from Brazil, 343.90 and 75 ct. Annealed green stones after cutting are not more than 20 ct. Exclusion is a stone from India, 80 ct. in the Nat. Hist. Museum, Los Angeles. There is a cut ametrine, 108.5 ct.
Legends. The popularity of amethyst as a talisman and an amulet is going from one generation to another among different peoples. Among its properties such ones were called: to protect against natural catastrophes, witchcraft and an “evil eye”. It was treated as a protective stone against hard drinking – Bacchus stone. May be because of its wine color – Greeks, who described such property of amethyst, didn’t like drunkards. It is supposed to protect from wounds, that’s why it is called also soldier’s stone. As a symbol of loyalty to a dead spouse, it is called widow stone. Violet color of amethyst should make the pain of soul and grief not so deep; it calms down and gives good thoughts. It is also treated as a stone of unshared love. Amethyst is connected with the Air, that’s why it is the best talisman for those, who were born under the sign of Aquarius. It is useful for spiritually developed persons, because it fills their aura with positive strength and good intentions. After the victory of Christianity over pagan cults, amethyst was devoted to the apostle Mathew. Astrologers treat amethyst as a stone of Pisces and Libra. Amethyst is regarded as a national symbol of Uruguay. In the U.S.A. it is an official gemstone of the Georgia State and of South Carolina; also in Canada – of the Ontario Prov.
Synthesis. In the early of 1960-s, at the Institute of synthesis of mineral rough materials, Alexandrov town, the Vladimir Region, an industrial technology of hydrothermal synthesis of amethyst with the method of it’s growing in thick alkali potassium solutions was worked out. Such crystals had uneven dispersion of color and abnormal pleochroism from reddish-violet to pale lilac. After ten years, at the same institute a new method of synthesis of amethyst from near-neutral solutions of ammonium fluoride was worked out. In that case, crystals are colored more even, they are not multicolored and they look more like natural amethysts. However, with any method the color depends on structural admixture of iron and it demands further gammairradiation to display it. As a development of those methods a technology of producing of synthetic ametrine was invented. Both technologies are accepted in other countries as well. Synthetic amethyst, unlike natural one, doesn’t change its color under annealing.
Synonyms. American synthetic dark-colored amethyst | American synthetic mean amethyst | Meta amethyst | Russian synthetic amethyst.
Imitations. It is difficult to make a mistake, mixing amethyst with other minerals because of its specific coloring. Among natural minerals there are visually similar: violet-rose spodumene – kunzite, vorobeyevite, spinel and violet fluorite. All of them are different from amethyst in hardness. Vorobeyevite and spinel are more hard, fluorite is less hard; spodumene differs in cleavage. As imitations of amethyst, they use synthetic materials: synthetic amethyst, synthetic garnets, corundum, spinel and glass, including barium glass and Japanese one – meta-amethyst.
Rose quartz (Rosenquarz—Rose quartz—Розовый кварц) variety of quartz (See quartz). There are two types of rose quartz, which are different in morphology. The first one is genuine rose quartz – it has pale rose or rose-red color; it exists in massive vein forms in pegmatites. Its color depends on admixture of titanium (Ti3+), it is also unstable and can weaken in sunlight; but some deposits give material with stable color. For rose star quartz it is typical to have regular oriented microcrystalline inclusions of rutile, which produce asterism in the shape of a six-radial star. Such inclusions can produce also the Tindal effect in the form of opalescence and lavender color. Quartz of such color has the trade name – lavendine. For rose quartz it is typical the effect of dichroism, and in cabochon – the effect of cat’s-eye. Sometimes, rose color of quartz can be a result of inclusions of the thinnest needles of dumortierite. The second rose quartz exclusively from hydrothermal veins in the form of crystals of light rose color. For difference from its massive version is offered to name rosa quartz. Its color depends on structural admixture of phosphorus (P5+), it is unstable and gradually weakens, and after heating under the temperature over 200˚C it disappears. It is known mainly in America; in Europe such quartz is found almost never.
Deposits. In Russia the best rose quartz was extracted in Karelia, in the Loukhskiy Dist., where the deposits Malinovaya and Nikonova Varaka, Pirt-Ostrov, Lissiy Bor and others are situated. The thicknesses of quartz cores in pegmatites reach 10 m. there; and they are formed to the half with rose quartz. In its transparent parts asterism was observed. A defect of rose quartz from Karelia is stripped dispersion of color and it’s fading. In the Altai Mts., pegmatites with rose quartz are known in the Tigeretskie Belki (Ridge), in the beryl-holding pegmatite of the Razrabotnaya Mt., where blocks of opalescent rose quartz, up to 1.5 m wide, were extracted. In the Irkutsk Region, near Slyudyanka, there is a deposit of rose quartz in pegmatites – Pad’ Asiamovskaya. In the Chita Region, pegmatites of the Sakhanai deposit in the Duldurghinskiy Dist. are perspective for the extraction of rose quartz. In the Ukraine, in the Dnepropetrovsk Region, there is the Sholokhovskoye deposit with rose quartz, which is represented with a vein up to 18 m. thick in the largest parts. In Uzbekistan and Tadzhikistan, rose quartz is found in pegmatite veins of the Turkistan Ridge. In Uzbekistan, similar veins are situated in the upper reaches of the Lyailik River, Fergana Region. In Kazakhstan, in pegmatite of the Kent deposit crystals of rosa quartz were found, as well as amethyst veined quartz. Near Ust’-Kamenogorsk, in the Kalbinskiy Ridge there are pegmatites with rose quartz at the Dungalinskoye deposit and in pegmatites of the raremetal Targinskoye deposit. In South Kyrgyzstan, in the Turkestan Ridge, there is the Asan Usan deposit of rose quartz. In Mongolia, the of rose quartz Ghurvan-Angalag deposit is in pegmatites.
Large deposits of rose quartz are in Namibia, Kenya and on Madagascar – near the settlements of Sahanivotry and Lac Alaotra. In India, the extraction of rose quartz was held in the states of Assam, Andhra Pradesh in the region of Warangal; Madhya Pradesh – in ChhindvÇra, and also in the states of Orissa, Punjab and Tamil NÇdu. In Finland the source of rose quartz was pegmatite veins in many regions of the country.
Crystals of rosa quartz in U.S.A. at the Mt. Mica mine and later in Whispering Pines quarry was first found, also at Newry and Red Hill, Oxford Co., Maine. In Brazil, rosa quartz was extracted in Minas Gerais from pegmatites Piabana and Araçuaí, near Governador Valadares; also in the region of Itinga: at Lavra da Ilha and the Ademar, near Taquaral; also at Alto da Pitora mine, near Galiléia. At the Sapucaia do Norti deposit, near Linopolis city, druses aggregates of rosa quartz crystals, up to 4 cm. long, were found with phosphates in small geodes. In the Bahia State, crystals of rosa quartz were found at the deposits Ribeiräo do Largo and Macarani. In the Paraíba State, rosa quartz was extracted at the deposits Alto Feiho and Manteno. In pegmatites of the Espírito Santo State and others, where processed rose quartz often performs asterism and the effect of cat’s-eye. In Nicaragua, rose quartz in pegmatites of the Serro Las Guavas deposit is found. Canada sends for the market rose quartz with asterism from the deposits of pegmatites of the Ontario Prov.
Synonyms. Rose quartz – False hyacinth | Asteriated rock crystal | Asteriated quartz | American ruby | Bohemian ruby | Mont Blanc ruby | Star stone.
Cut Gems. Transparent rose quartz sometimes is cut, weight of stones is not more than 20-30 ct., but more often it is used in cabochons as insets for jewelry. In 1891, at the Kolyvanskaya lapidary factory from rose quartz a saltbox and a plate (37 cm. in diameter, 1 cm. thick, weight about 4 kg.) were made. In the State Hermitage, SPb. there is a pair of egg-shaped vases, 28 cm. high, from rose-white quartz from Tigeretskie Belki Ridge, Altai Mts. Balls are often made from rose quartz. Such ball with asterism, made from Brazilian material, is kept in the Smiths. Inst., Wash., its weight is 625 ct.
Legends. Rose quartz is a talisman of healthy and happiness. As an amulet, it helps to avoid stress. Astrologers think that it is a lucky stone for those, who were born under the signs of Taurus and Capricorn. In Tibetan medicine it is supposed to be a stone, which stimulate heart activity. In the U.S.A., rose quartz is an official symbol of the South Dakota State.
Synthesis. At the Inst. of Experimental Mineralogy, Chernogolovka, Moscow Region, a synthetic analogue of rosa quartz enough good for jewelry purposes was produced.
Imitations. Imitations for rose quartz are known from alabaster colored with aniline dyes.
Chalcedony (Chalzedon—Calcédoine—Халцедон) (Agricola, G. 1546), after Chalcedon or Calchedon (now Kadi-Kiei) near Istanbul. According another version the name was made after Carchedon, Gk. translation of Carthago – a port in North Africa through which chalcedony was transported.
Composition & Properties. Oxide – SiO2 n•H2O. Cryptocrystalline, fine-fibrous variety of quartz. Hardness 6.5-7. Density 2.3-2.6. Here the main varieties of chalcedony are described: agate, carnelian, chrysoprase, plasma and chert. Forms of existing of chalcedony in the nature are represented with filled amygdales in effusive rocks, crusts and nodules, flat-layer accumulations. Amygdales can be completely made with chalcedony with kidney-shaped surface and even in the form of stalactites. Chalcedony has typical bedding structure, which is obvious after coloring or gamma-irradiation. In common chalcedony it is clear in agates, in figured chert, carnelian, less – in chrysoprase. Massive sintered chalcedony with spherical texture has its own name – chalcedony agate, gray glass head or chalcedonite. Stripped variety of chalcedony, formed with filling hollow places in lava through rhythmical-zonal crystallization, is usually called agate. The shape of amygdales and geodes of agate often explains its names – geode agate, loaf agate, tube agate, starred agate or botryogen agate which looks like a bunch of grapes. The most exotic shape of a triangular, a star or a square is observed in amygdales of agate in rhyolites, so called star-shaped agate, and in the U.S.A. there is also a local Indian name for such amygdales – thunder eggs agate. Amygdales of chalcedony with pimpled surface are called toadstone, and in Japan chalcedony in flat nodules is called abakus stone. The middle size of amygdales in cross-section is 5-12 cm., maximum up to 2 m. Amygdales of chalcedony with closed residual geode, partly filled with water solution, are called water stone, hydrolite, world-eye, anhydros. Walls of chalcedonic amygdales or geodes usually are encrusted with quartz or amethyst crusts. Amygdales of chalcedony, filled with quartz, are called quartz agate, and with quartz-calcite – calcite agate.
Half-transparent and translucent chalcedony is called common chalcedony. Its color is even, grayish-white or bluish-gray. Many kinds of chalcedony were called earlier agates. It is obvious in the following examples: transparent light gray – glassy agate, red – blood agate or meat agate, dark red – crimson agate, dark blue-red – pigeon blood agate, translucent black – black agate or black onyx, translucent white with opalescence – chalcedonic moonstone, translucent milky-white – white agate or white carneol, non-transparent white – chalcedonic cacholong, and light blue – blue chalcedony, sapphire agate or sapphirine. This rare dark blue or light blue variety of chalcedony is classified only in Russian gemology. At first, this name for chalcedony was used but R.J. Hauye in 1817. However, Germ. mineralogist K.W. Nose gave this name to the mineral, which was classified later as haüyne, and in 1819 the same name was given to a new mineral from Gk. So, to avoid mistakes and misunderstanding, better call this kind of chalcedony just blue chalcedony. There is a supposition that blue color of the stone sometimes depends on inclusions of fine-fibrous zircon. White-light blue chalcedony from the Oregon State, the U.S.A., with silver-white aventurescence is called Oregon moonstone. In foreign literature we can see such names of colored chalcedony as amberine – yellow or yellow-green, Aztec agate – purple one from Mexico, damsonite – non-transparent violet, cesvik – bright rose, laguna – pale violet, massic – translucent gray, mtorolite – translucent emerald-green and containing chromium, fairbern – coral-red.
Spotty kinds of chalcedony are widespread; their color often depends on mineral admixtures. So, moss agate contains treelike dendrites of manganese. Because of various patterns it can be called differently (See syn.), and if there are white inclusions in it, its name is white moss agate; if there are multiple inclusions of flakes of goethite, lepidocrocite or hematite, which look like red spangles, its name is fire agate or hemachate. If such flakes are regularly oriented, it can be called aventurine agate. Translucent, uneven colored spotty chalcedony with inclusions of different shapes and various colors is called flower agate or lace agate. Depending on the size and the color of spots it has different names. With red, brown or yellow spots it is polka dot agate or goat’s-eye.With dim brownish inclusions of goethite it is chalcedony tiger’s-eye or tiger’s-eye. Gray chalcedony with red spots of cinnabar is called myrickite or myrickite agate. Greenish-blue one with chrysocolla is called azurlite, azurchalcedony, quartz chrysocolla, chalcedonic chrysocolla or jeweller’s chrysocolla. Green one with inclusions of malachite is called prasmalachite.
According the character of inclusions in chalcedony such kinds can be classified: cloud agate, plume agate or plume chalcedony – with stalactite-like inclusions, oolitic agate – with oolites of calcite, sagenitic agate or straw agate with inclusions of mineral needles, which form lattice or net, and with paniculate inclusions – horse-tail agate. Coral agate or lace agate – it is tube-shaped chalcedony, which looks like corals, it is filled with spherical zonal-festoon aggregates of brownish-red chalcedony and colorless or milky-white comb quartz. White chalcedony with sectors of comb aggregates of quartz, which look like frosty patterns, is called – frost agate or mat stone. Not rare it can be found incrustations and pseudomorphs of chalcedony on other minerals and fossil materials: timber – wood stone, shells – shelly agate, corals – coral agate or starred agate, ammonites – beekite or zoésite. Polyhedrons of chalcedony, which have linear borders, are the results of the replacement of plate materials such as anhydrite, barite, calcite, as well as fluorite and zeolites with chalcedony. Non-transparent to translucent stripped chalcedony with inclusions of country rocks is called jasp agate. It is a transition kind of chalcedony to a country rock.
Synonyms. ~ Agate: Kandy ~, chalcedony ~, honey ~. | Aegophtalmos, Germ. chalcedony with eye structure | Anthrax, obs. | Cerachates | Chalcedonagat | Chalcedonite | Oriental chalcedony, trade name for high quality rough material; opposite to it occidental chalcedony – trade name for low quality rough material | Massic | Californian moonstone | Prismatic moonstone | Murrhina, anc. Roman | Fibrous quartz | False sapphirine | ~ stone: eagle ~, horn ~, Mokka ~, Stephen ~, St Stephen’s ~.
Enhydros, from Gk. rich with water – Aperture agate | Water agate | Hydrochalcedony | Hydrolite | Water stone.
White chalcedony – Babagury, Old Russ. | Milky agate | Cacholong | Leucagate.
Blue chalcedony – Eldoradoite, after the discovery location in El Dorado Co., California, the U.S.A. | Blue chalcedony | Mojave blue chalcedony | Blue moonstone | Sapphirine, from Gk. “sappheiros” – blue gemstone, after its color | Sarduin | Mecca stone, from Arabic | Zarafina.
Chalcedony rose to purple. ~ chalcedony: amethystine ~, purple ~, red ~, rose ~ | Coralline, because of its similarity with red coral | Damsonite, from Arizona, the U.S.A. | Fairbern, after the discovery location near Fairburn, South Dakota, the U.S.A.
Chalcedony red-brownish – Akinph, obs. Russ. | Cambay stone | Pramnion, from deposits of India, by Agricola | Wackler, obs.
Chalcedony yellow – Waxy agate | Amberine, from Engl. amber, after its color | Canary stone, obs. | Capercailye stone, local name in Evenkia, Russia | Ceragate, from Lat. “cera” – wax, after its color | Canary chalcedony | Wax chalcedony | Yellow chalcedony | Demion, obs. | Jaspis, obs. | Leontine | Lyncury, Old Russ.
Green chalcedony – Heliotrope agate | Chromechalcedony | Green chalcedony | Cromchalcedony | Keystoneite, obs. | Star malachite | Matorolite (matorodite, mtorolite, mtorodite) after the discovery location near Mtoroshanga in South Rhodesia (now Zimbabwe) in 1967 | Prasius, by Agricola.
Chalcedony spotty with mineral inclusions: ~ agate: cobra ~, dendritic ~, cat’s-eye ~, Indian ~, landscape ~, moss ~, black moss ~, green moss ~, Montana moss ~, mosquito ~, picture ~, plume ~, point ~, pudding ~, river ~, sagenitic ~, from Latin “sagens” – fishermen net; scenic ~, seaweed ~, sweetwater ~, after the discovery location on the Sweetwater River, Wyoming, the U.S.A.; treelike ~, vegetable ~ | Calbenite | ~ chalcedony : Kazakhstan ~, landscape ~, mossy ~, pea ~, point ~ | Dendrachate | Diskagate | Moss jasper, mist. | Mokkam | Mokkastein, Germ. | Muschelachat, with a pattern as a shell | Stephanik, gray with red spots | ~ stone: amarllo ~, a figured variety from Texas, the U.S.A.; dendritic ~, landscape ~, Mocha ~, Mokka ~, after the Arabian center of trade with gemstones Mokka (now Mocha near Aden, Yemen); mosquito ~, moss ~, (by mistake from Mocha stone).
Agate (Teophrastus, 372-228 B.C.), after the Agates River (now the Karabi River on the southwest of Sicily Is., Italy). More truthful is the origin of the name from Old Semitic “akik”, after the oasis in Saudi Arabia; where in the 3d millennium B.C. agate was extracted. Perhaps, it is the source of Arabic akik – carnelian, Pers. chackik. There is also a version about the origin of the name from Gk. “agates” – magical, excellent (Lucas Ben Serapion), must be, because agate served as a talisman. Agate is a regular-stripped kind of chalcedony. According the patterns of its bedding, they classify flat parallel and zonal-concentric agates, not rarely containing opal, quartzine and other varieties of quartz. Amygdales of agate can be filled with crystals of rock crystal or amethyst – amethyst agate, crystal agate, drusy agate or geode agate.
In the reign of Solomon (965-928 B.C.) agate was called shebo (from Hebrew “sheba”) after the biblical name of Saba in modern Yemen”. Agate onyx decorated the throne of Solomon. Onyx is mentioned in the Bible more often than other stones. In Torah it was called shoham, Teophrastus called it onyxion, and Pliny the Elder called it onyxion or onyx gemma. In ancient Indian lapidaries it was called gemma – and this name was later transferred to all the precious and semiprecious stones, this is the source of the term gemology. Parallel-bedded agates or cameo agates are the perfect material for glyptic. According the color of the layers, they are classified into: chalcedony onyx – with light blue-gray layers, rainy agate, cacholong agate or opal agate – with white layers of opal, amber agate – with yellow layers, sardonyx or sardagate – with brown-white layers, carnelian onyx – with red-white layers, Arabian onyx or zebra agate – with black and white layers, chert agate or Algerian black onyx – with gray and dark layers. The second kind of agates is zonal-concentric one. It is widespread, especially in Brazil, that’s why it is called Brazilian agate. Often alternation of layers, up to 8,000 and more for 1 cm. thick, leads to the moiré effect and iridescence in agates. It is typical for fine-bedded rainbow agate or moiré agate. With red color it is called fire agate. Contrast colored black and white layers are typical for Arabian onyx, yellow and white – for ceragate, brown and yellow – for carneol agate, red and white – for carneol onyx, brown and white – for sardonyx, gray and rose – for rose agate, white and gray or bluish – for chalcedony onyx. Black or dark brown onyx nicolo contains light blue and white layers, and dark gray is called Algerian black onyx. Alternation of layers of white opal with black chalcedony is typical for button opal or button onyx, as well as for opal agate. For bastion agate it is typical a similarity of pattern of its bedding with plans of fortifications. Texture specifics of zonal-bedded agate are reflected in the names of its kinds: distributing block agate, breccia agate, coral agate, feather-like agate, fragmental agate, macaroni agate, mosaic agate, pagoda agate, polycentric agate, ring agate, roe agate, shelly agate, zigzag agate, ruin agate or polyhedral agate. With pairs of “eyes” stone is called agate owl’s-eye. Changes of colors and complicated patterns are typical for fancy agate, shining agate or crazy’s agate. We should also mention red-brown agate with exquisite pattern of white veins, which is called in the U.S.A. Montana-agate, also gold agate with inclusions native gold and silvery agate with inclusions native silver.
Synonyms. ~ agate: apricot ~, crazy’s ~, from Gk. “krasis” – mixed; Cretan ~, chrysocolla ~, Dryhead ~, after the deposit Dryhead, Montana, the U.S.A.; dull ~, Egyptian ~, frost ~, Lake Superior ~, after the discovery location near Superior Lake, Michigan, the U.S.A., and the same one in Canada – Duluth agate and Keweenan agate; lavender ~, occidental ~, oriental ~, roll ~, salmon ~, Serra massic ~, syn. colored Serra stone., Sicilian ~, starry ~, Thrace ~, | Sardiy | ~ stone: flower ~, frost ~, pagoda ~, sard ~, Serra ~, from the Serra do Mar deposit, Brazil.
Bastion agate: ~ agate: Brazilian ~, circle ~, Cyclopean ~, eye ~, fortification ~, fortress ~, topographic ~. | Owl’s-eye | Ox-eye | Wolf ’s-eye | Fairburnit, from South Dakota, the U.S.A. | Aleppo stone, after the discovery location near Halab (form. Aleppo Khabat), Syria | Ribbon stone.
Iridescent agate – Iris agate | Lamellar agate.
Onyx from Gk. – fingernail – Laminated agate | Panther agate | Ribbon agate | Black chalcedony | Nogat, Old Russ. | Chalcedonyx | ~ onyx: agate ~, Arabian ~, banded ~, blue ~, colored; oriental ~, stripped ~, Uruguayan ~, zebra ~, Indian.
Carnelian. Carnelian is the name for transparent chalcedony, even colored in orange-red or body-red color. Besides, there are such names as carneol, from Lat. “carnis” – meat, or “cornum” – cornelian cherry or cornel, because of its meat-red color; and sarder – auburn-brownish or tawny. We should agree, that there is no obvious difference between these kinds; the color can be slightly different in one piece of stone. Its color depends on iron oxides in micro pores. Usually it is thicker near the surface and weakens to the inner sectors. Till the 18th cent., in the literature red and brown chalcedony was called only sard – after Sardis, the capital of ancient Lydia in Asia Minor; and according another version, from Arabic sard – yellow. In the Middle Ages, orange-red carnelian was treated as a female stone, and brown-red one – as a male stone. Mentioned in those times mystical stone lyncur or lyncury many specialists suppose to be carnelian, but there is also an opinion, that it was yellow or light brown tourmaline.
Synonyms. Acint, Old Russ. name of carneol | Carnelian, after cornelian cherry or cornel | Semi-carnelian | ~ carneol: beryl ~, obs., kadnos ~, obs.; Kambey ~, after the Indian port Kambey, from which carneol was exported, occidental ~, onyx ~, yellow ~. | Carnelian onyx | Sandy sard, of spotty color | Sardik, 12th cent., obs. | Sardion,4th cent., obs. | Sardios,10th cent., obs. | Sardius, obs. | Sardonyx,11th cent., obs. | Serdonich,14th cent., obs. | Smazen’, Old Russ.
Chrysoprase (Pliny the Elder, 77 A.D.), from Gk. “chrysos” – gold and “prasios” – leek-green, after the color. Translucent, bright green kind of chalcedony, which was classified by Leman in 1775. Usually it contains admixtures of opal, nickel up to 3% because of fine-dispersed inclusions of nickel-containing minerals: talc, saponite and serpentine. The color of chrysoprase and its variety – artificially colored green onyx – changes from pale green, lemon-green to dark green and bright blue. Blue chrysoprase sometimes contains inclusions of chrysocolla. Admixture of manganese forms black dendrites in chrysoprase. Chrysoprase with inclusions of country rocks is called chrysoprase matrix. Green chromium-containing chalcedony from Zimbabwe, opposite to chrysoprase, is called usually green agate or green chalcedony, as well as artificially colored chalcedony. The coloring components in chrysoprase and Agate are inclusions of nickel-containing variety of saponite – pimelite.
Synonyms. Citric chrysoprase | Chrysoprasus, anc. Gk. | Australian jade | Queensland jade | South Pacific jade | Praser. Germ.
Plasma, from Gk. “plasma” – cut stone, because it was used often for small stone carving. Plasma is nontransparent or merely translucent kind of chalcedony, colored in different tones of green. Its color depends on dispersed micro inclusions of green silicates: amphiboles, seladonite and chlorite. Not rarely they are represented as white or yellowish spots. Plasma with red spots or stripes, depending on admixture of oxides, has its own name – heliotrope, from Gk. “Helios” – the Sun and “tropos” – turn, because if a stone with red spots is put into water an effect appears, as if a small Sun is turning around.
Synonyms. | Blood stone | Brokatstein, Germ. | Blood jasper | Oriental jasper.
Chert, Russ. name from Gk. “kremnos” – rock, cliff or from Lat. “cremare” – to burn, because it has used for striking fire since ancient times. Nontransparent, brownish, sometimes with patterns variety of cryptocrystalline silica, rich with mineral admixtures. According the content they classify opal, opal-chalcedony, quartz chacedony and quartz-chert. Besides, among the minerals of the group of quartz it is quartzine, which is often exists in them. Sometimes, in the caves of chert there are found small quartz and amethyst crusts. Chert is found as concretions and seams in sedimentary rocks. For large spherical and cylindrical concretion of chert they use the special Engl. term – paramoudra. Formation of chert in sedimentary rocks is connected mainly with secondary rocks of silica from the remains of silicate organisms. Blanket varieties of chert come into siliceous schists, phthanites and hornstones. Concretions of chert reach 70 cm. and more in cross-section. According their color, they are classified into monochrome and figured chert or stripped chert. Sometimes, they contain shells, sea-urchin skeletons and other bioorganic remnants as inclusions. The most typical admixtures in chert are minerals of the group of quartz: tridymite, cristobalite as well as calcite. Almost always there are admixtures of iron oxides, mainly hematite. They give brown color to chert. An example of ornamental chert is Prairie agate in the Nebraska State, the U.S.A. Its color varies from bright red and yellow to pale tones of light blue, tawny-brown and gray.
Because of their high hardness, beautiful patterns and excellent polishing ability cherts are used as ornamental stones.
Synonyms. Ferrous chert | White chert | White jasper chert | Eolite | Firestone | Flint, black | Hezite – opal-chalcedony chert | Keratite | Kiselstein, Germ. | Kornit, Germ. | Ognevik | Flint pebble | Opal pebble | Silexite | Horn stone | Zinopel.
Deposits. Formation of chalcedony is connected with hydrothermal process as well as with chertification and diagenesis of sediments. Its deposits are found in magmatic rocks, in weathering crusts, in sedimentary rocks and in placers. Because of a great amount of chalcedony deposits we will mention only the most important ones, where the best ornamental varieties exist. In Russia, on North Timan, agate deposits have been being excavated since 1936. There are: Chayachiy Mys (cape), Levaya Ievka River and others on the rivers Belaya and Malaya Chiornaya. Agates in basalts exist in amygdales, up to 0.5 m. in cross-section, up to 50 kg. Color of Timanian agate is light gray with bluish tone; fine-stripped varieties with moiré effect are not rare, too. In the region of Arkhangel’sk, in the Plisetsk Dist., on the Onega River, there is the Onezhskoye deposit of figured chert. It is represented with concretions of different shapes; their average size is 10x12x7 cm. Its color is mainly light and stripped; thickness of stripes is about 0.5 cm. In the Moscow Region and in the Vladimir Region, deposits of figured chert are found in carbonate layers: Golutvin, Dmitrov, Stupino and others. Average size of these accumulations is 0.6x0.4 m., rarely up to 1 m broad. Color and patterns of chert are rather decorative. Inside big concretions not rarely there are caves with small stalactites of chalcedony, up to 12 cm. long and 1.5 cm. in cross-section. Inner surfaces of such caves are covered with quartz crusts. In the Northern Caucasus, in the region of Cherkessk, the Jegutinskoye deposit of gray-blue chalcedony was discovered in limestones as well as linked placers. The most part of this chalcedony should be colored. In South Urals, in the Chelyabinsk Region, near Magnitogorsk, in trachyliparites there is the Magnitogorskoye deposit of agate of concentric-zonal structure, often in jasper “covering”. Its amygdales reached 15 cm. in cross-section and 3 kg. In the Polar Urals, to the north from Labytnangi, on the Kharbey River, there is known a lens-veined type of Kharbey agates with color zones. In the northern part of the Krasnoyarsk Region, in the basin of the Lower Tunguska River, in basalts there is widespread agate mineralization, mainly in the form of small amygdales. In Buryatia Rep., in Western Transbaikalia there is the Tuldun deposit of agate, where agate, carnelian, chalcedony pebbles up to 20 cm. in cross-section and jasper pebbles up to 40 cm. in cross-section were extracted. In Buryatia Rep., near Gusinoye Lake there is also a deposit of agate and dark blue chalcedony – sapphirine. Placers of chalcedony, carnelian and agate were discovered in Eastern Transbaikalia, along the rivers Argun’, Shilka, Onon and on Toreiskie Lakes. Their chalcedony was found also in rock deposits, such as Mulina Gora. In the Amur Region, placers of carnelian and agate were exploited in the basin of the Zeya River at the Burundinskoye and Norskoye deposits, along the rivers Nora and Burunda, and also in the basin of the Selemja River. At all these deposits resources of carnelian were calculated; the size of its pebbles reached 20x10 cm., content in placers was up to 2.4 kg./m.3 . An interesting variety is tube agate, which consists of multiple small stalactites with tube channels among them. In the Khabarovsk Region there is the Yadrinskoye deposit of agate in tuffs. In Primorskiy Region, to the north-east from Nakhodka, the Sergievskoye deposit of agate is discovered. In Yakutia, placers of agate, carnelian and chalcedony are described in the basins of the rivers Alazeya and Kolyma, including the Mustakhskoye deposit of agate and carnelian on the Alazeya Plateau. There fluidal-spherical lavas contain orange carnelian, red and raspberry-red carneol with non-clear concentric pattern. More rarely they find parallel-stripped agates with alternation of white, red, reddish-brown and black layers. On the Chukchi Penin., 80 km. to the east from the Egvikinot village, near the Gulf of Cross, there is the Kandymiveem carnelian deposit. At the same region, at the Leningradskiy mine, quality agate was extracted; and near the Chaunskaya Bay, in the lower reaches of the Kremyanka River, the resources of jewellery-ornamental carnelian in placers were calculated. In the Magadan Region the north from Magadan knows agates on the Ol’skoe Plateau, in the upper reaches of the Ola River. There, in amygdule-stone basalts, not only amygdales of agate up to 5 cm. in size are found, but also roundish or ellipse-shaped mineralized geodes up to 1 m. in cross-section. They can be filled with chalcedony and agate, and sometimes with crystals of quartz and calcite. Bank placers of chalcedony and agate are found on the Bering Is., in the group of the Commander Iss.; in the northern part of Kamchatka near the capes Cape of Tevi and Cape of Kakhtan; in the northern part of the Sakhalin Is. near the Gulf of Peltun; on the Kurily Iss. – on the Moneron and Shikotan Iss.
In Belarus, deposits of chert-flint are exploited in the Grodno Region. In the Ukraine, in pegmatites of Volhynia, there are sintering formations of chalcedony enriched with inclusions of goethite. After cut they perform golden-yellow, yellow-brown color; they look like tiger’s-eye. After polishing they have chatoyancy and can be evaluated as ornamental stones. In Crimea, agate and carnelian were found on the rivers Alma and Kacha, as well as in the Karadag Mt., which became a national park. In Georgia, the deposits Pamachskoye, Tedzamskoye and Shurdo are exploited; they contain calculated resources of chalcedony and agate. At the Pamachskoye deposit the size of tube amygdales of agate reached 5 m. In the north of Armenia, the deposits Ijevan, Sarigyukh and Kalininskoye with agate including white agate were discovered. At the deposit Ijevan, there is the best ornamental agate of all the Caucasus exists. It has clear concentric-zonal pattern with alternation of bluish-gray and white layers. In Azerbaijan, there are the deposits of agate: Adzhikend, Alinzachay, Todan and Eyvazly. Chalcedony at these deposits performs in amygdales up to 15 cm. in size. At the deposits Todan and Eyvazly significant volumes of heliotrope were extracted; its accumulations reached the size 15x5x5 cm. In Northern Tadzhikistan, near Adrasman, in limestones they find Akkurskoye deposit rare varieties of agate of blue, egg-yellow and black color. In Kazakhstan, in the desert of Betpakdala, Zhezkazgan Region, at the Alatakyr deposit, they extract landscape chalcedony with dendrites of iron and manganese.
In Great Britain, the most famous agate placers are situated on the seacoast of Scotland. In Germany, numerous accumulations of agate are found in rhyolites and quartz porphyry of Saxony. They can be observed from the Erzgebirge, Saxony, to the northwest, to the Harz Mts., Lower Saxony. One of such deposits is St Egidien, Saxony. In the north-western part of Bavaria there are known conglomerates with agates. In the western part of the country, near Idar-Oberstein, Rhineland-Palatinate, agates were discovered even in the 14th cent.; in 1454, on the base of these deposits the center of stone cutting was organized. Among the most ancient chert deposits of Europe, we should mention places of its extraction on the Rügen Is. in the Baltic Sea, near the Germany coast. In 1740, in Poland, one of the first deposits of chrysoprase was discovered – Baumgarten, near Sobcovice-Slenske (form. Frankenstein), Lower Silesia (Dolny Âlàsk). Till nowadays, it is completely worked put, but at the same region, near Wroclaw, in nickel-containing weathering crust two new deposits of chrysoprase were opened – Sklyary and Wiry, Wojewodztwo Slaskie (Upper Silesia). In the southern part of Poland, in the Kraczewskie Mts., there is the agate Nowy KošcióΙ deposit. It is linked with places of changes in rhyolites and represented with veins of chalcedony and amygdales of agate, up to 1 m. in cross-section. In Czech Rep., the North-Czech Region, the deposits of agate of the Kozákov Mt. near Levin are exploited; in Moravia there is the deposit of plasma – Grubsice. Since the 18th cent., in Romania, a large deposit of blue chalcedony the Trestia has been known. Among other deposits, we should mention Gurasada, Tâtârâšti and others with amygdales of chalcedony, up to 40 cm. in cross-section. At the deposits Tisovi¸ t ˘ a and Baia Nou˘ a, in the region of Banat, chrysoprase is extracted. In Slovakia, there are such deposits of chalcedony as Slanec and Tri Vody, Karpatian Mts., as well as those of agate – Kwetnica and Sološnica, Male Karpaty. In Bulgaria, the agate Madzharovo is in the south-eastern part of the country, in the East Rodopy Mts, and the most perspective among the rock deposits is Studen Kladenets, 25 km. to the east from Kyrjali. Amygdales and lens-shaped caves in andesites filled with agate reach there 1 m. in length. Beside agate there are crystals of quartz, calcite and other minerals on the inner surfaces of these caves. In former Yugoslavia, in nickel-containing weathering crusts of Kosovo there is a chrysoprase deposit near Priština; and in Vojvodina, at the Fruska Gora deposit agate onyx with opal and jasper is extracted.
In 1964, in Tadzhikistan, on the southern slope of the Kuraminskiy Ridge, in the Adrasman area, the Akkurskoye deposit of agate in conglomerates was discovered; and at the Tavakskoye deposit in limestones black agate was found. In Turkmenistan, chalcedony and agate are found in the region of Nebitdag at the Kafikshem deposit, and at the Bol’she-Balakhanskoye deposit. In Central Kazakhstan, at the deposits Sarykulboldy, Novo-Akkermanovskoye and Pstan translucent chrysoprase in the shape of veins up to 20 cm. thick is extracted from weathering crust in serpentinites. In Pribalkhashia, at the Itmurundy deposit, there is chalcedony of dark gray color with places of sealing-wax tone; it is enriched with inclusions of fine-dispersed hematite. In East Kazakhstan, there are many agate deposits: Ayaguzskoye, Sartmolla, Semipalatinskoye, Pavlodarskoye, Kyzyltogan and others. In 1958, in South Kazakhstan, in the Small Karatau Ridge, the Dzhambul group of deposits of rose Dzhambul chalcedony was discovered, there, at the Alatakyr deposit landscape chalcedony was extracted. These deposits are linked with the horizon of chert in sedimentary layer. Isolations of chalcedony are represented with concretions, lenses up to some hundred meters long, up to 2.5 m. thick; and also with layers of chert, which can be observed at the distance of several km. Content of chert is heterogeneous, mainly quartz-chalcedony. Color is often black, gray, yellowish and rose, more rare – thick red, lilac and brown. In the same sedimentary layer accumulations of petrified wood of quartz-opal content are found. In Kyrgyzstan, in volcanic rocks of the Turkestan and the Chatkal Ranges, agate is found at the deposits Dzholbar, Taldy-Bulak and Achik-Tash. In the Fergana Valley, there is the Sary-Tash deposit of chalcedony. In Mongolia, main deposits of agate are represented with placers, including large deposits of agate chalcedony: Dalan Türüü, Ulegei Khid, Cho-Fe; sapphirine up to 20 cm. in cross-section – the Gashuunii; carneol and plasma – the Ikhe-Jirgalantu (Orgil); nephrite-like white chalcedony – the deposit Sharpakhoit. In India, on the Deccan Plateau, in the states of Gujarät and Madhya Pradesh and in the Mahäräshtra State, there are the most significant deposits of chalcedony, including moss agate, onyx and carnelian. They exist in weathering crusts of basalts, in conglomerates and placers. In the Mahäräshtra State plasma is extracted, and near Poona – heliotrope. In the north-eastern part of India similar deposits are situated in the states of Bihär and Andhra Pradesh. Indian agates usually are artificially colored just after the extraction. In Iran the best heliotrope is extracted.
In African countries, deposits of chalcedony are known in Algeria, Botswana and Ethiopia. In Botswana, there is an apricot agate of pink color. In Morocco, at the Atlas Mts. there is the deposit of chalcedony and agate Marrakech. In Egypt, chert placers in the Nile Valley and the deposit of agate Djebel Abü Diiba have been known for 3,000 years. In Congo (Kinshasa), agate placers are situated in the basin of the rivers Kassay and Congo. In Malawi, in the Chikwawa area, there is a deposit of red agate. In Central Tanzania, beside agates, a deposit of chrysoprase and prasopal was opened in the region of Hanety Hills. Since 1950-s, in Zimbabwe, in the region of Mtoroshanga, a large deposit of chrome-chalcedony – matorolite or green agate has been being developed. In Mozambique, the deposit of agate Lebombo is discovered. In South Africa, agate is extracted as additional material at the diamond placers of the Vaal River. On Madagascar, in the region of Antsirabe, plasma is extracted. On the Arabian Penin., at the territory of modern Yemen there are the most ancient deposits of chalcedony, including the Sana’a deposit. They were exploited even in the times of the queen of Sheba, when agate and carnelian were sent to the king Solomon (965-928 B.C.).
In Australia, in weathering crust of serpentinites at the Marlborough Creek deposit, 100 km. to the northwest from Rockhampton in Queensland bright green and apple green chrysoprase has been extracted since 1963. Its veins are up to 20 m. long and up to 10 cm. thick. Bedding rocks of this chrysoprase deposit are transformed into massive quartz metasomatic. Because of its spotty color, which depends on inclusions of relict chromite, they are used as ornament’s stones under the trade name birbirite. In the same state, near the Mt. Hoy village, by Rockingham there is a deposit of spheroidal rhyolite or tropical wood jasper. It is metasomatic changed rhyolite, which is compound with sphaerolites of chalcedony with inclusions of chlorite. Color of this ornamental stone is greenish, in some places – reddish speckled one. In the central part of the Western Australia State, in the region of Undjeline, deposits of chrysoprase are linked with nickel-containing weathering crusts; and to the southwest, in the region of Northman, they are linked with “magnesite hat”. In the same state, on the plateau Antrim, in weathered basalts, to the north from Halls Creek, there are deposits of agate Mt. Herbert and others; at the Wanday Station deposit agate is extracted from sedimentary rocks.
Brazil possesses the most significant deposits of chalcedony, including agate in amygdales and amethyst. In the basin of the Parana River, a layer of agate-containing basalts has the square of development some 1.2 million km.2, and thickness 650 m. Thickness of some veins reaches 3 m. At the territory Rio Grande do Sul State there are three the most important regions with agate and amethyst: northern one in the upper reaches of the Uruguay River – mainly with amethyst, including the deposit Espimoso; central one in the region of Santo do Jacque – with agate; south-western one along the border with Uruguay – mainly with amethyst. There are three types of Uruguayan agate: in the shape of flattened amygdales with clear bedding, fine-bedded rainbow agates and unpleasant looking Umbu agate at the deposit Umbu. The latest ones are typical for river placers; they are usually colored before selling. The most part of agate amygdales have the size about 20-30 cm. in cross-section, some of them reach 1 m. and even more. In the Goiás State there is a chrysoprase deposit. In the north-western part of the country, in the Paraíba State, especial polyhedral agate – Paraíba agate is extracted. Formation of such flat-faced shapes of agate is connected with filling of caves among bedded crystals of calcite, which was dissolved later. In Uruguay, there are also significant deposits of chalcedony and rare rose agate with emerald-green veins is extracted. In 1900, the biggest amygdule of agate was found there, 10x2x1 m. in size. Besides, they often find here anhydrous agate – agate amygdales with liquid. In Panama, agate deposits are exploited, including moss agate and black agate. Mexico sends fire agate, lace agate, purple agate and blue agate to the world market, as well as jasper-like red-yellow chalcedony with greenish-blue parts of chrysocolla and brownish ones of limonite. This ornamental stone has bright spotty color, that’s why it is called – parrot wing, parrot feathers or chrysocolla chalcedony. In Mexico, in the Chihuahua State, at the deposits Galiego, Villa Aumado and Ojo Laguna fine-stripped and bright colored agates and carneols are extracted.
In the western part of the U.S.A. – in Oregon, Montana, Idaho, Nevada and California, there are numerous deposits of different kinds of chalcedony. In Oregon, in rhyolites of the Canyon Sucker Creek, amygdales of agate are extracted, which are known under the name thunder eggs. They are of spherical forms – lithophysae with mineralized central caves. The shape of these caves after cutting often has star contour. Their walls are formed with agate, often with carnelian. There is also the Priday Ranch deposit of agate and numerous findings of petrified wood and figured jasper, known as Biggsian jasper were made. It is volcanic ash of dark blue color, filled with chalcedony. At another deposit plates of pudding agate with black and tawny spots on light yellow background is extracted, as well as another variety of the same stone – pudding fire agate with inclusions of goethite, which give bright colors and iridescent tones in agate. Besides, in this state there are deposits of moss agate, myrickite, anhydrous agate and chrysoprase. In California, at the Little Mule deposit and at others, blue chalcedony, moss agate, fire agate, rose flower agate, myrickite and heliotrope are extracted. In 1878, in the Tulare Co. in weathering crusts of serpentinites, at the Sierra Nevada Mts., the deposit of chrysoprase Venus Hill has been discovered as well as others. The best chrysoprase was extracted near Portville; there was also a deposit of sierranite – an ornamental stone, which consists of agate onyx and chert. In the same state, in Santa Clara Co. unusual concretions of chert of bright red, yellow, green and brown color were found, this stone was called scareian jasper. The same name was given to a variety of chert with inclusions of cinnabar at the New Almaden mine. In Arizona, near Duncan, famous fire agates with rainbow iridescence are extracted. There was also a deposit of amethyst-like large-blocked chalcedony – damsonite was found; its pieces were up to 100 kg. At the Globe Miami mine, jeweler’s chrysocolla was extracted – it is chalcedony of sky-blue color. In the north-eastern part of this state, at the deposits Saddle Mt. and Pointed, in the area “National Park of Petrified Wood”, was found trunks up to 20 m. long and 1.5-2 m. in cross-section. Petrified wood has red, yellow, blue and purple colors there; it is an ornamental material. Sometimes, there are caves inside trunks, their inner surfaces covered with crystals of rock crystal and amethyst. In New Mexico, in the region of Santa Fe, there is the “Country of agate” – large deposits of ornamental varieties of agate on the Rio Chama River and near Yangonville. In Montana, at the Dryhead deposit, they extracted Dryhead agate in nodules up to 10 cm. in cross-section with stripped structure. More often they are colored in different tones of red, rose, orange with light blue-gray layers. In the valley of the Yellowstone River, a tributary of the Mississippi River, placers of agate are situated. Ornamental Montana agate is found there – picturesque variety of moss agate with complicated patterns of red-brown and black dendrite inclusions. In Wyoming, there is a deposit of moss agate of gem-quality, so called sweetwater agate, which is characterized with dendrite inclusions of the star shape. In North Dakota, there are deposits of high quality moss agate. In Nebraska, bright red and yellow ornamental variety of stripped chert is found, which is called prairie agate. It was chosen as an official symbol of the state. In the western part of Kansas, there are deposits of moss agate. In Texas, they find Texas agate or plates of pudding agate. In the eastern part of the U.S.A., in Minnesota, the most popular ornamental stones are agates from Superior Lake. In Michigan, on Isle Royal (Superior Lake), on the bank placers, wonderful Lake Superior agates are found. Their outer zones consist of carneol, and then there are layers of red, orange and white color, which come into zones of blue and green color. Rose color depends on admixture of native copper, and blue one in iridescent layers – on inclusions of bornite, in greenish-yellow layers – on chalcopyrite, in green ones – on carbonates of copper, in black ones – on tenorite, in orange ones – on chalkotrichite, and in tawny-red layers – on cuprite. In Ohio, beautifully colored chert from the Flint Ridge deposit is known as an ornamental stone; in Missouri – mozarkite, a variety of multicolored chert, which looks like agate. It is an official symbol of the state. Its color is blue-gray, rose or pale lilac with stripes of red, yellow and orange color. In the Washington State, near Ellensburg, there is a deposit of blue gem-quality agate. Weight of some amygdales reached 5.5 kg. In Arkansas, an ornamental stone novaculite is extracted, it is formed with small crystals of quartz, cemented with chalcedony. An ornamental variety of brecciated novaculite is characterized with more bright color – from yellow, orange and bright red to black one. In the eastern part of Canada, bank placers of agate are exploited near Fandy Bay, Nova Scotia; and also on the Graham Is., British Columbia. In the south-eastern part of Cuba, on the northern slopes of the Sierra Maestra Range, agate-containing conglomerates are found.
Ornamental rocks. Among silicate rocks, which are used as ornamental stones, we should mention the following: hornstone, silexite, phthanite, siliceous schist, opalescent jasper and chalcedonite. In Crimea, Ukraine, there is known a rock formed with onyx agate and chert. Its analogue in the U.S.A., California, is sierranite, which is called so after the discovery location at the Sierra Nevada Mts. In the process of formation of chrysoprase deposits in the ultrabasic rocks in the lowest zone of the weathering crust their silification is going with the replacement of rock-forming minerals with chalcedony. As a result, massive rocks of tawny-brownish and violet-red color appeared – birbirites, which are called after the discovery location on the Birbir River in Ethiopia.
Quality improvement. Artificial coloring of chalcedony was known even in Ancient Rome. It reached the largest scale in Germany among the masters of Idar-Oberstein, Rhineland Palatinate. The technology of coloring wasn’t radically changed. The easiest way is the impregnation of chalcedony in the solution of sugar or honey during a week with following processing with sulfuric acid and annealing. Changing the regime of this processing they can receive stable black or brown color. Another method is the impregnation with iron salts with following annealing or light heating. It gives red or yellow color. The impregnation with chromium or nickel salts with following heating or annealing gives green color. The impregnation with yellow bloody salt with following boiling in the solution of copper vitriol gives dark blue or light blue color – false lapis lazuli, agate turquoise. The color of carnelian strengthens through annealing less than 150°C, especially with admixture of hydrochloric acid. Weakness of these methods is the long duration of processing, but without it the deepness of coloring is significantly less. Aniline paints are also used but they give not so stable colors. Instead of the solution of sugar, they often use nitrobenzene. With this method of quality improvement of chalcedony there is no special need in modern technologies of coloring through irradiation. After coloring agates receive new names: black agate, green onyx, Turkish agate, blue agate or onyx. Chalcedony artificially colored in green is called – chrysoprase, Swiss jade or jasper jade, emeraldine; in blue – lapis or German lapis lazuli, Swiss lapis lazuli, Italian lapis lazuli, false lapis lazuli, as well as blue moonstone and blue jasper. Chert of chalcedony and carbonate-chalcedony content are also processed through coloring in black, brown or green color. Quartz-chalcedony and calcium-magnesio chert can’t be colored.
Cut Gems. The widespread gemstone in archaeological excavations is chalcedony in multiple varieties. Adornments and amulets from it were popular in all the social classes of ancient societies of the Old and New World. Antique glyptic was growing on chalcedony; and the level of its development was unprecedented. Each noble Greek or Roman had his own carved stamp. The symbol of authority of the Roman Emperor – the scepter – was decorated with an eagle’s head from chalcedony. In the Grün. Gew., Dresden, in Germany, many vases and bowls from chalcedony made by German masters are exhibited, including the luxury decorated bowl “Bath of Diana”, 38 cm. high, with the figure of Diana from ivory. In the 17th cent., in Russia, in the workshops of the Moscow Kremlin, exquisite snuffboxes, stamps, dagger-hilts, bottles and cups were made from chalcedony. Similar work of art made by Chinese and European masters of the 18th cent. are exhibited in museums throughout the world. Masters of the firm of K. Fabergé also used chalcedony and its varieties in their things. From this material many figures were cut, which are kept in the collection of the British Queen now. In the collection of the State Hist. Museum, Moscow, there is a brooch from the firm of K. Fabergé, made by A. Holmström, with perfect moss agate and ruby, framed with brilliants. In the State Hermitage, SPb., there is a ring with a sapphirine gem, which performs a flying heron, which was made by Dexamen Khiosz (5th cent. B.C.). Blue chalcedony was popular not only among antique masters. In Mongolia, working at the decoration of the Palace of Weddings in Ulan Bator, a designer Munhtogtokh made a mosaic picture in the center of which a legendary flower of East was depicted – a lotus. Its petals were made from blue chalcedony – pure and tender as a young bride.
Agate was often used in jewelry and in glyptic in ancient times. Beads, insets for rings, earrings, brooches, stamps, cameos, figures, bowls and cups were cut from it. In antique times, rulers collected bowls and cups from agate. Mithridates possessed more than 4,000 works of art. Samples of such things with agate we can see in any museum. The biggest sculpture is 2 m. in height statue of Buddha from black agate (1st cent. A.D.) was found at the excavations in Djorjar in India in 1980. A unique work of art from the whole agate is kept in the Kunst. Hist. Museum, Vienna; it is a flat plate, 75 cm. in diameter. The most valuable piece of agate is in the temple of Kaaba in Mecca. It is black and white onyx agate, 24 cm. broad, which is cemented into the wall of the temple opposite the entrance, 72 cm. from the floor. Once this stone was changed for the price of the whole island. The biggest cameo in the world – “Big Cameo of France”, 31x26.5 cm. in size, is made on 5-layered sardonyx; it is kept in the Cabinet More of medals in the Louvre, Paris. Two Emperors with their retinue are depicted on it. More than 20 figures are carved on it with jewelry exactness; they form three horizontal belts. This cameo is dated to the early of the 1st cent. A.D., the reign of the Emperor Tiberius, the successor of Augustus. In the State Hermitage, SPb., more than 20 thousand gems are kept, including the biggest collection of antique gems on agate an a unique gem on sardonyx – “Cameo Gonzaga”, 15.7x11.8 cm. in size, on which Egyptian King Ptolemy II and his sister Arsinoya are depicted. This rare example of big portrait gems of the Hellenistic epoch (3rd cent. B.C.) was propriety of the Dukes Gonzaga (Mantua, Italy) till 1630. After many other possessors Josephine Bogarné, the wife of Napoleon, has bought it for 1.5 million franks. In 1814, she gifted the cameo to the Russian Emperor Alexander I as a sign of thankfulness for his generosity to her after his victory over Napoleon. A unique masterpiece of the Renaissance was a gold bowl, which was gifted to the Russian Emperor Peter the Great by the Danish King. On the surface of the 32 cm. height bowl there were about 2,320 fragments of chalcedony carved by Ital. and Fr. masters. This bowl was destroyed in fire; only some stones were saved. They are in the collection of the State Hermitage, SPb., now. In the 16th cent., Russian masters-stonecutters made unique pieces of glyptic. Among them are breast signs for bishops from onyx agate where Oranta and St John the Ladderer were depicted; they are in the collection of the Armory Museum Kreml., Moscow. In the 18th and 19th cent., masters from the Urals made from agate not only copies of antique cameos, but also many different pieces of art. Among them, there are snuff-boxes, stamps and cups. Such cup from crimson agate was gifted to the Japanese Emperor in the early of the 20th cent.. In the beginning of the 19th cent., in the epoch of Alexander I, agate was in fashion, and work of art from it were often decorated with brilliants. In 1900, for the World exhibition in Paris masters from the Urals have made “The Map of France” using different kinds of agates, carnelian, Shaitan perelift and jasper.
Carnelian is one of popular stones for many peoples of the world, especially in Egypt, Asia Minor and Middle Asia. In the antique times, it was treated as sunstone. In ancient graves multiple adornments from carnelian are found. On the territory of modern Iraq (1500 B.C.), in a king’s tomb, a gold diadem with carnelian was found. In the tomb of the Pharaoh Tutankhamen, who ruled in the 14th cent. B.C., among other gold and precious work of art, several things from carnelian were found: an amulet in the shape of a snake, a pendant-pectoral in the shape of a heart and a carved figure of a legendary bird Ment with the Sun disc on its back. Adornments with carnelian are often found in the Scythian barrows of the 7-6ss cent. B.C. In the State Hermitage, SPb., there is one of the most ancient gems of the Cretan-Mycenae epoch (4th cent. B.C.) with a hunting scene carved on carnelian. From carnelian an idol of a pagan god Khubala was cut. His statue was in the temple of Kaaba before the accepting of the Islam, but it was destroyed according the order by Mohammed (570-632), when he had taken Mecca. Carnelian was often used in glyptic; especially it’s stripped variety – sardonyx, which was popular for signets, stamps and snuffboxes. Carnelian was a favorite stone of Arabs, who carved citations from Koran on it. The prophet Mohammed had a signet from carnelian. In the Christian world, sardonyx was dedicated to the apostle Phillip; the apostle Bartholomew, who spilled rivers of blood, received bloody-red carnelian as a personal symbol; St Jacob – tender chalcedony. In the Kunst. Hist. Museum, Vienna, there is the “Gem of Augustus” made on sardonyx, it is an antique cameo by the Roman master Dioscorid. The Greek master Diodor made another famous cameo with a picture of a lyre among bees on sardonyx from Samos. Benvenutto Chellini (1500-1571) carved a scene from the Gospel – the Last Party – on parti-colored carnelian; he used different tones of that stone to perform the characteristics of persons. This gem is kept in the Cathedral of St Peter in Rome now. In the Grün. Gew., Dresden, there is a vase from sardonyx called “Dragon with Medea”, 30 cm. high, made by the German master Dinglinger. Signets with carnelian served as talismans for G. Byron, A. Pushkin and S. Esenin
Chrysoprase is the most precious variety of chalcedony. In the Middle Ages, it was used in the socalled “Karlstein mosaics”. In Czecia, in the Cathedral of St Vitus., Prague, the chapel of St Vaclav is decorated with such mosaics with chrysoprase, and in the castle Karlstein near Prague – the chapel of St Catherine. Since 1740, an intensive exploiting of chrysoprase has been being begun in Silesia. The King of Prussia Friedrich II (1744-1797) compounded a big collection of work of art from this stone in San-Souse Palace in Potsdam, by Berlin. There is a pair of small tables with mosaics from chrysoprase, 60x90 cm. in size. Work of art with chrysoprase was in the great fashion in the 16-18ss cent. Nowadays, this stone is still in fashion. It is processed as cabochon and as flat insets for jewelers.
Heliotrope. The Crucifixions was often carved on it, because its red spots symbolized drops of blood of Jesus Christ. That’s why heliotrope was used mainly for decoration of church utensils. It was put into priests’ crosses and medallions. In Germany, in the Grün. Gew., Dresden, there are wine-goblets from heliotrope made by Czech masters (1600), 10.3 cm. high and 14.5 cm. in diameter.
Chert was widely used in the culture of Central American Maya. They had signs of rank cut from it. For example, a figure of a noble man with a knife in his hand; an adornment in the shape of an exquisitely carved square plate with human heads in the corners; a dagger with a hilt in the shape of a feathered snake and others. At Russian exhibitions, jewelries from Moscow chert are often exhibited.
Legends. As an amulet, chalcedony can protect its holder from anxiety and melancholy. It is a lucky stone for those, who are born under the sign of Capricorn. Different peoples supposed agate to be an amulet, which saves its owner from poisons, thirst and also from storms. “Eye” agates are popular as amulets against “black eye”. Agate with three “eyes” was evaluated as the most precious, it was called trioftalm (Fr.). According legends, the goddess Juno – the protector of women – had earrings from such agate. Similar earrings were presented to Penelope by one of her fiancés. Agate was used to heal wounds and to stop cramps. In the antique times, they believed, that to strengthen the healing power of agates it would be necessary to carve symbol of illness on them. Special inscriptions were also carved, for instance: “run away, gout” and others. As a talisman, agate stimulates spiritual awakening, it calms psycho, prolongs life, strengthens vision and hearing, develops speech abilities. Agate is one of the 12 stones, mentioned in the Bible. Christians treat it as a stone of the apostle John. Astrologers describe it as a stone of planets Mercury and Venus. It is linked with Air and it is especially good for those, who are born under the signs of Taurus, Aquarius, Cancer and Libra. Agate is declared to be an official symbol of several states of the U.S.A.: Montana, Minnesota, South Dakota, thunder eggs agate – Oregon, blue chalcedony – of South Dakota, chert – of Ohio, prairie agate and agate chert – of Nebraska. Agate onyx is supposed to be an amulet against “black eye” and witchcraft. At the East, it is a stone of grief and deep sorrow. Other peoples treat it as a leader’s stone and a talisman of politicians. It strengthens memory and protects from murder. Astrologers believe onyx agate is a lucky stone for those, who are born under the signs of Taurus, Cancer, Leo, Virgo and Capricorn. Heliotrope symbolizes courage and wisdom in India. As a talisman, it can awaken fantasy and help in bringing up children. As an amulet, it helps to avoid wounds in battles, to free oneself from anxiety and melancholy. Astrologers treat heliotrope as a stone of the Sun and as a lucky stone for those, who are born under the signs of Cancer and Sagittarius. Carneol, according ancient legends, is an amulet against illnesses, conflicts, enemies’ intrigues and witchcraft. As a talisman, it strengthens sense of touch; it is a stone of truth, love and faith. Christians believe that red carneol is a stone of the apostle Bartholomew. Astrologers treat carneol as a stone of Fire. Its planet is Mars. It is a lucky stone for those, who are born under the signs of Aries, Taurus, Cancer and Scorpio. Carnelian was dedicated to the goddess Isida in Ancient Egypt. In Europe, it was a talisman of love and faith. In Russia, it was supposed to be a love talisman. According astrologers, it belongs to Air. Its planets are Jupiter and Venus. It is a lucky stone for almost all Zodiac signs, but especially for Taurus, Capricorn, Libra and Virgo. In ancient chronicles carnelian was described as a healing stone. Now, its high effectiveness in healing of wounds is proved. Carnelian is a symbol of Sweden and Norway. Chrysoprase is a stone of hope, success and wisdom. It is a talisman against “black eye”, envy and curves. Astrologers believe it is a lucky stone for those, who are born under the signs of Aquarius, Sagittarius and Capricorn.
Similar Gemstones & Imitations. Common chalcedony looks like opal, smithsonite; carnelian – like jasper; heliotrope – like variscite, jadeite and nephrite; chert – like jasper. The widespread imitation of chalcedony is glass, for example agate glass, in which it if easy to create necessary color, structure characteristics, admixtures and so on. In cheap adornments stone carving can be also used.
Opal (Opal—Opale—Опал) (Pliny the Elder 77 A.D.), from Gk. “opalios” – striking an eye, Lat. “opalus” – charming the vision, Sanskrit “upala” – noble stone. Mineraloid from the group of quartz – SiO2•H2O, content of H2O in noble opal 5-8%. Hardness 5-6.5. Density 1.8-2.3. Glass luster, greasy, waxy and pearls one. Very cracked. Amorphous. All the variability of opals, according their ornamental properties and value, can be separated into two big groups: noble and common opal. Prevailing forms of classifying of opal are sintering aggregates. Beside them, there are concretions or forms of filling of caves – including, veins and crusts. Bedding rock, full with veins and opals inclusions, is called opal matrix. In Western gemology such rock is called opaline. It can be processed as cabochons or flat insets. In the nature, pseudomorphs of opal after bioorganic fossils are not rare. In bamboo sometimes isolations of bioorganic tabasheer opal are found. Opal differs from other minerals with amorphous form, globular structure; which is obvious only under an electronic microscope. Its main properties depend on the size and the shape of globules – spherical isolations of silica. According the level of regularity of its structure such varieties are classified: A-opal – with the most solid package of globules; C-opal – the most solid package of globules of amorphous silica with inlaid spheroid’s of cristobalite; CT-opal or potch – package with numerous defects because of the presence of cristobalite and tridymite crystals. A-opal and C-opal are classified as noble opal, and cristobalite-tridymite opal (CT-opal) – as common opal. Noble opal is formed mainly with amorphous opal, the most regular package of globules and similar characteristics are typical for it. According the calculations, the speed of accumulation of the thinnest layers of noble opal was 1 mm for 20,000 years. Space among globules is filled with amorphous silica. Such three-dimensional structure leads to diffraction and interferential of the light, which is the direct reason of bright iridescence of opal, or, as it is sometimes said, – “opalization”. However, the latest term sounds similar with opalescence – the effect, which is produced only by diffraction of light. That’s why more general term is more good – iridescence. In the rare cases, there is asterism in the shape of three- or six-radial star in opal, and sometimes the effect of cat’s-eye in cabochons. The size of opal globules has the direct influence on the character of its color reflexes. When globules are 150-200 nm – violet patches of light prevail, when it is 300-350 nm. – green ones, when 400-450 nm. – red ones. Several colors can co-exist in one stone. Criteria of quality of opal are brightness and deepness of its color, play of color, pattern and transparency. The color of opal depends also on admixtures. Red and brownish to black color depends on oxides and hydroxides of iron and manganese. Some other colors depend on mineral admixtures: oripiment, hematite, graphite, chlorite, celadonite and others. For common opal irregular package of globules is typical, as well as differentiation of their sizes and shapes. Spherical shape of globules often transfers to polyhedral one. Beside hydrated amorphous silica, among these globules pore water exists. Silica can come into fibrous cristobalite and tridymite. And even more, in the most part of common opals globules are formed with cristobalite. These properties of structure lead to weak translucency and absence of iridescence. If in noble opal polychromatic iridescence is typical, for transparent varieties of common opal milky-bluish opalescence is characteristic – as a result of the effect of Tindall. In Ceylon opal opalescence is completed with chatoyancy as in moonstone. For bluish or reddish girasol opal, which is called also opal fish-eye, wavy alternation of color is typical. In Harlequin opal from Australia inclusions of parallel-fibrous crocidolite lead to chatoyancy, so called opal cat’s-eye or crocidolite opal. In cabochons of fire jade the effect of cat’s-eye depends on inclusions of parallel-fibrous aggregates of alkali amphibole – grunerite into opal. Sometimes, such effect appears because of fibrous aggregates of chrysotile, as it can be observed in yellowish-green and yellowish-brown opal cat’s- eye from Brazil. In that role rhodusit exists in opal hawk’s-eye from the Kumoly deposit, Kazakhstan. Asterism, which is observed in opals from the Spenser mine, Idaho, the U.S.A., is a rare example never seen at other deposits.
Noble opal,or precious opal is half transparent or translucent, light bluish-gray or light colored with bright play of color – rainbow iridescence. Transparent to translucent variety of it with strong iridescence was called rock crystal opal. One of the brightest samples of noble opal is polychromatic harlequin opal with mosaic iridescence. According the shape and the color of iridescent parts, the following varieties are classified: clover opal – with green parts in the shape of a clover leaf, ribbon opal – in the shape of long ribbons, palette opal – looks like colors at an artist’s easel; fiery rain opal – looks like rays of the setting sun on the wavy water surface; Lluvisnando opal from Mexico and also fish scales opal and flower opal. Additionally pin fire opal is classified – with irregular points of red and green iridescence on the ruby-red background. Its variety is flashing opal with iridescence in the shape of fire flash of one color, and also point wise fiery opal – with iridescence of different colors in the shape of spots or points. A unique variety of noble opal is king’s opal or tsar’s opal with concentric-zonal iridescent color, red in the center, then, green and colorless near the edge. We should mention especially transparent, almost colorless to light bluish-greenish opal and also amber-yellow to hyacinth color fire opal with bright red play of color. Because of this effect, it is used sometimes for faceting. Close in color to this variety it is another kind – golden or gold opal with iridescence of yellow tone. Milky-green variety of noble opal with bright green or carmine iridescence is called Lechosos opal in Mexico, and its orange variety is called fossil orange or sunflower. The most precious variety of noble opal is black opal, usually it is Australian opal not always of black color – sometimes it is dark gray, dark blue, dark violet with bright play of color in red or green tones. Its black color can depend on admixture of graphite. Intermediate variety to black opal it is butterfly opal of dark colors with bright and strong iridescence. Opposite to black opal specialists classify white opal with iridescence in light blue tones. This name is accepted for a group of light colored noble opals. In Brazil, a rare variety of noble opal is known – contra lus opal, transparent, looking like pale bluish milky water opal with golden tone, which possess a property to perform play of color not only in reflected light. Water opal as it is, or jelly opal, is usually transparent with iridescence, which looks like a soap bubble. Girasol opal is bluish, translucent, with reddish reflexes in bright light. Night opal possesses the strongest iridescence in artificial light. Onyx opal with alternation of layers of noble opal with chalcedony of different colors. Oolite opal with oolite-like inclusions has unusual iridescence. Seam opal is the widespread form of isolations.
Common opal or semi-opal is widespread. It is weakly translucent to non-transparent, without color iridescence, it often contains admixtures. Australian miners use special name for such opal – potch opal.As ornamental material, we should mention varieties of bright color or with interesting pattern. There is: red – rubolite, apple green, translucent – prasopal, nickel-containing – chrysopal, chromium containing – green opal, wax-yellow or yellow-brown – wax opal and polluted with admixtures – isopyre. Transparent hyalite opal is widespread and is used in jewelry; it is colorless or even colored, pale blue, pale green, yellowish, and also hyalite fish-eye. Spotty polychromatic hyalite is called azules opal. Hyalite is found in the places of coming out of hot springs. Together with geyserite and non-transparent white hyalophane, or hyalophane opal it produces scum, so called pealite. Such porous opal is called also nectilite, when dry it sticks to a tongue. In water it, as well as hyalophane, becomes transparent or translucent with weak play of color, that’s why it is called chameleonic stone.
Cacholong is popular jewelry-ornamental material highly evaluated in the East. White to yellowish, nontransparent cacholong is called porcelain opal or milk semi-opal, and if it has dark admixtures in treated cracks it is called web semi-opal. Translucent variety is called milk opal. In manganopal ornamental pattern is produced with dendrites of manganese. Sometimes, dark brownish with pitch luster pitch opal or ferrous opal is also classified as an ornamental stone; it is found in the form of nodule, where it is partly comes into chalcedony. It is also known as liver opal, menilite opal and menilite or fire stone. Opal of smoky color with inclusions of organics or other admixtures is called radio opal or rauchopal. Among common opals there is also wood opal or woodstone, which was formed as a result of replacement of timber with opal. Usually it’s happened with conserving of all the structural elements of timber. Sometimes, such pseudomorph is regular colored, but more often it is yellowish-brownish with pitch luster. Pseudomorph of opal on serpentine is called opaline, and mixture of opal with nontronite – fettbol. At fossil opal animal bones, skeletons of freshwater creatures and seashells replaced with opal are classified. We should mention also opal of plant origin mascareignite – it is amorphous silica, which is formed in some species of bamboo. Bamboo opal or reed opal is white to light bluish-white, it looks like hydrophane. It is weakly translucent or non-transparent and has a trade name tabasheer or bamboo pearls.
Mineral admixtures which produce unique ornamental characteristics of opal raise its commercial value. Let’s observe them in the sequence of mineralogical systematic. Fine-dispersed native copper produces color in Peruvian pink opal. Oxides and hydroxides of manganese, mainly romanéchite, produce dendrites in dendritic opal or moss opal. Admixture of halloysite and variscite is typical for allophan opal. Another clay mineral nontronite produce green color in chloropal or corencite, in the Ukraine such opal is called Ungvárite. In opal cristobalite, beside nontronite, there is admixture of cristobalite. Pelicanite, which is formed in the process of weathering of feldspars, consists of mixture of opal with kaolinite. Rose opal, enriched with inclusions of palygorskite, is called angel’s skin opal. In the process of replacement of serpentine with opal siliciophite is formed. Opal with inclusions of red cinnabar is an ornamental variety of vermilite. Orange-yellow opal – forcherite contains fine-dispersed inclusions of orpiment. In Peruvian blue opal there is admixture of chrysocolla, which gives it the color. Ornamental opal with hematite, impregnating roots of acacia; in Great Britain, it has a trade name – jedi opal. Parallel-fibrous inclusions of asbestos-like amphiboles or chrysotile produce the effect of cat’s- eye in opal cabochons. So are amiante opal, crocidolite opal and chrysotile opal. Sometimes, opal replaces rose-like and stalactite-like aggregates of gaylussite, glauberite and gypsum. These ornamental pseudomorphs are called fossil pineapple or pineapple opal because of their typical shape. Partly silicification, non-transparent ferrous opal is found as red-brownish concretions. Similar type of opal, polluted with admixtures, is known as menilite. Its tuber-like masses in salt-watered marls contain admixture of cristobalite.In cryolite, because of admixture of opal, porcelanous ornamental variety is produced. Onyx opal or opal agate is characterized with alternation of layers of opal and chalcedony. Ferrous opal is sandstone with cement from noble opal. Opal consists of skeletons of radiolarian and diatomaceous, which form thick layers of siliceous sedimentary rocks diatomite, opoka and tripoli, – they are used in jewelry as fine abrasive materials.
Deposits. In the nature, noble opals of two genetic types are found: hydrothermal – in effusive rocks, and exogenous – in ancient weathering crusts. In 1985, in Russia, in the Primorskiy Region, in the upper reaches of the Alchan River, the only large of noble opal Raduzhnoye deposit was discovered. It is a deposit of hydrothermal type in argillized and opalized breccias andesites. Opal is represented there as insets, veins with thick parts up to 5 cm., and amygdales up to 20 cm. Light colored gray opal dominates, as well as orange and milky-white. Another variety is colorless transparent opal, rarely colored into amber-yellow tones with hydroxides of iron. In transparent opal complicated dendrites and inclusions in the shape of white flakes can be often observed. At the other deposit of the Primorskiy Region, Sergeevskoye, in the valley of the Razdolnaya River opal pseudomorphs on wood are found, sometimes there are complete trunks of petrified woods. In the West Sayan Mts., there is the Idjimskoye deposit of cacholong, and in Tyva – a deposit of prasopal. In 1988, in the Tomsk Region, on the large territory numerous places with different varieties of opal were found in the form of veins up to 25 cm. thick, and nodules, including the placer Mirninskoye with noble opal. In the South Urals, at the Khalilovskoye deposit, light green semi opal with serpentine is extracted as additional material. At the Aydirlinskoye deposit, clay minerals gibbsite, allophane and others with admixture of NiO up to 30% are found in glassy opal of turquoise color – aidyrlite.
In the Ukraine, there are non-industrial places of common opal in weathering crust of andesites and granites. In Zakarpats’ka Region, to the north-east from Uzhhorod and near the village of Kol’chino, Mukachëvo Dist., opal and semi-opal perform veins in andesites, up to 20 cm. thick, and isolated nodules up to 2 m. in cross-section. These opals have green color because of rich inclusions of nontronite; they are called Ungvárite. In the Vinnytsya Region, near the villages of Lyulintsy and Glukhovtsy, there are pelicanites with veins of non-transparent Kiev opal, up to 20 cm. thick. In pegmatites of Volhynia black opal was found; their color depends on admixture of bioorganic substances. And near Kazatin, there are solid ornamental pelicanites – mixture of opal with kaolinite. In Kazakhstan, in the region of Aktiubinsk (Aqtöbe), in weathering crust of the Kimpersaiskiy massif of serpentinites, there are numerous places of green and blue opal and semi-opal. They form veins, small nodules and lenses, up to 0.5 m. thick. Opal, different in color, mainly non-transparent to translucent and more rare to half-transparent is found there. In 1962, to the south from Kökshetaü (form. Kokshetau), in the region of MakÏnsk, in pelicanites the deposits Voznesenskoye and Kara-Agach with fire opal, moss and black opal were discovered. Their defect is the presence of cracks, which is the result of dehydration. In the Qaraghandy (form. Karaganda) Region, semi-opal was found at the Kok-Zaboi mine, dendritic opal – at the chrysoprase Pstan deposit, wood opal – at the Shokpaktyozek deposit, cacholong – at the chrysoprase Sarykul-Boldy deposit. To the southwest from Qostanay (form. Kustanai), at the Zhetiqara deposit, opalized magnesite and serpentinite with dendrites of oxides of manganese and iron were extracted. In East Kazakhstan, there is the Nikolaevskoye deposit of opal. In West Uzbekistan, in the Qyzylqum Desert, there are cacholong deposits Kul’dzhuktau and Taskazgan. Large accumulations of cacholong in weathering crusts are known at the deposits Ak-Tash and Saryktau – in the south-western part of the Bukantau Ridge, and also at the deposits Aytym and Tulantash, in graphited schists, near Tamdykuduk, in the Alatau Mts. Cacholong is represented with nodules and lens isolations up to 30 cm. thick. Its best kinds have significant part of chalcedony content.
In Slovakia, there is the opal deposit of hydrothermal type – Dubnik near Çervenica, 18 km. from Prešov. It has been exploited for 1000 years till 1922. Earlier it was in Austria-Hungary, that’s why opals from this deposit were called Hungarian opals. They extracted hyalite, hydrophane together with noble opal there. Nowadays, in the eastern and central parts of Slovakia, new opal deposits are opened near Badín, Yasteb, L’ubietová, Horlyany and Drahov. In Hungary, opal is known at the Erdöbénye deposit, near Sorenc; and green chromium-containing opal was extracted. In Austria, in the Styria, near Knittelfeld, orange-yellow opal – forcherite is found, which contains fine-dispersed inclusions of oripiment. In France, findings of opal are known in the Menilmontant region, near Paris, and at the Quinci deposit, Essonne, also rose opal – in Mehun-sur-Yèvre, Cher. In Turkey, prasopal was known even from the times of ancient Lydia. Now, it is extracted at the Kütakhya deposit, near Simav. In Poland, at the deposits Sklyary and Tomice, in opal-chalcedony veins they find nickel-containing prasopal, and in cracks in serpentinites near Jordanów – hyalite, Wojewodztwo Dolnoslaskie. In Germany, hyalite was extracted near Freiberg, Baden-Würtemberg. In Denmark, on the Faeroes Iss. – fire opal; in Iceland – geyserite. The best hyalites were found in Czech, at the Valeç deposit.
Among African countries, almost non-transparent fire opal is extracted in Ethiopia. Here, in the Shewa Prov., in the Menc Gishe Region, a deposit of opal is known, where opal has wonderful play of color from colorless to white, blue, orange, gray or brown. Recently, to the south from Berberï one more deposit of noble opal was found, up to 15 km. long. In Tanzania, deposits of nickel-containing prasopal is exploited in the region of Hanety Hills. On Madagascar, in the south part of the island, near Beraket, there is a deposit of fire opal, and near Tsivory – a deposit of yellow-green opal.
In Australia, deposits of opal in weathering crusts dominate, but there are also deposits of hydrothermal type. Nowadays, Australia is the main supplier of noble opal, which sends to the market about 80-95% of the world extraction. The first findings of opals were made there in 1849. The main deposits of opal are situated in the south-eastern part of the country; they are linked with weathering crust of chalk rocks of the Great Artesian basin. In 1880, in New South Wales the White Cliffs deposit was discovered, and in 1901, at the same region – the Lighting Ridge deposit. In 1914, in the southern part of the country the largest opal Coober Pedy deposit was discovered, and in 1930 – the Andamooka deposit. Opal mineralization is observed there in 5-30 m. deep from the surface. In Queensland, deposits Kannamulla Paru, Kynuna, Opalton and Eromanga are exploited. There pebblian opal, or boulder opal was found. It exists inside silica-ferrous concretions up to 20 cm. in cross-section, which are called “Job’s nuts”. At the Heyrix deposit concretions with opal reached 3x1.2 m. in size. There also sandstone, or pipe opal is found, which has the secondary importance. This name is used for opal veins in kaolinized sandstones out of opal concretions. In New South Wales, some opal deposits are linked with effusive rocks. Noble black opal is extracted at the deposits Lighting Ridge and Andamooka only. There also beautiful pseudomorphs of opal, perhaps on glauberite, are found in the shape of radial-rayed joints of needle crystals. At the Coober Pedy, deposit noble opal pseudomorphs on fossil wood were found in pieces up to 5x3 cm. in size. Here, in 1972, the biggest boulder opal, 16 kg., was found. In Western Australia, to the north-east from Laverton, fire opal is extracted; at the Manxman deposit near Bullfinch – white opal; at the Widgiemooltha deposit – red-blood opal; at the Kalgoorlie deposit – yellow opal; at the Yarra Yarra deposit – Yarra-yarra opal with the effect of cat’s-eye. Among other countries, we should mention black opals of Indonesia, but there is an opinion that they are subjected to dehydration like Mexican black opal and after a while began to crackle. On Sri Lanka, greenish-yellow opal cat’s-eye is extracted; in Vietnam, the opal deposits Thiuse, Kannack, Phú Hiên and Dakmin are known. In Japan opals are found in the Fukushima Pref. at the deposits Ishikava and Tatyama, in hot springs, hyalite opal is found. On the Taiwan, greenish-blue chrysocolla opal of gem-quality with fine inclusions of chrysocolla is found.
Brazil takes the second place in the world in extraction of milk noble opal with bright iridescence. It is extracted in the states of Piauí, Bahia, Ceará and Rio Grandi do Sol. In the Piauí State the deposits Boi Morto and Rio Corrente are exploited. The first of them is characterized with a broad spectrum of colors of noble opal, including fire opal and opal cat’s-eye. At the second one, noble opal, because of inclusions of hematite, iridescent in blue, green and red tones. In the Rio Grandi do Sol State opal is found in agate-containing sedimentary layers. Its partly rolled pieces from placers are of orange-red to fire-red color; they have 50-70 gm. In the Bahia State, to the north-east from Vittoria da Conquist, near Fazenda Bredjina, a deposit of half-transparent green opal in veins of chalcedony is found; it has ornamental quality. Pieces of opal reached their 10 cm3 .
Mexico is known with its famous fire opals, white milk opals and black opals, and also with hyalite. Fire opal of bright yellow, orange or red color is extracted from cracks and caves in volcano lavas at 150 small deposits in the states of Guerrero, Jalisko, Hidalgo, Queretaro, Nayarit, San Luis Potosí, Chihuahua and others. Opal was known there even in the times of Aztecs state (1325-1521), which called it humming bird stone. After the Spanish invasion, opal deposits were forgotten, and the largest Juan Del Rio deposit in the Querétaro State was rediscovered in 1855. Industrial exploitation of the Djurado mine was opened only after the World Was II. The maximum weight of separate isolations of Mexican opal usually is not more than 50 ct., rare findings reach the weight of 93.12 ct. Because of its transparency, it received the name glass or crystal opal, and because of its high popularity in Japan – Japanese opal. However, Mexican fire opals and yellowish-red opals from the Querétaro State loose their color with time, that’s why in Europe there is a prejudice against them. In Honduras, in the Gracias a Dios Dept., is the best deposit in transformed volcanic rocks with pearls-gray noble opal, possessing red iridescence. In Peru, at deposits of the Andes Peruvian blue opal, or Andean opal is extracted; it contains admixture of chrysocolla, which form its color.
In the U.S.A., there are numerous deposits of noble opal. The first of them was discovered in Idaho in 1890. There was also opal pseudomorphs on wood are found – wood opal. To the east from this deposit, in the Bitterroot Mts., the Spenser deposit was discovered a bit later; now it is famous with the finding of star opal. This bluish-green or orange-red opal forms in caves of obsidian and perlite. Among the most significant deposits of the Nevada State there is the Rainbow Ridge, near Virgin Valley. It was discovered in transformed volcano tuffs in 1905. Opalized fossil woods and animal bones are found buried in them. In Louisiana, there is the deposit of noble opal Cedar Grove. There opalescent sandstone with noble opal in the cement content is used as an ornamental stone. In Oregon, at the Opal Beauty deposit, in bags inside perlite they find contra lus opal with iridescence, which is seen against the light. In Canada, in the British Columbia Prov., at the Okanogan deposit, near Vernon, opal was extracted, including fire opal.
Unique findings. The biggest noble opals were found at Australian deposits. In 1912, in Queensland, an opal 4,100 ct. was found. In 1956, at the Coober Pedy deposit, an opal “Australian Olympian” was found 17,700 ct. (3.54 kg.), 25.4x14x12.7 cm. in size, it was evaluated in $1.8 million. In 1988, there was also found an opal “Jupiter-5”, 26,350 ct. (5.27 kg.), 23x12 cm. in size. Later, on the same deposit an opal, 82,500 ct. (16.5 kg.) was extracted, which was evaluated in the sum more than $5 million. But the recent finding became a champion – an opal “The Panther”, 306,500 ct. (61.3 kg.) it was separated into three pieces: 36, 11.3 and 9 kg. At the Lighting Ridge deposit several large opals were found. The biggest one was “Pat’s Stone”, 8.9x7.6x0.6 cm. in size and 1,418 ct., which was extracted in 1956. Then, there was a black opal “Flamingo”, 800 ct. In 1915, an opal “Empress”, 212 ct., was found. In 1922, one of the most beautiful opals was found – “Red Admiral”, or “Butterfly”, some 50 ct., with iridescent pattern looking like a butterfly. Besides, at the Lighting Ridge deposit unique black opals were found: “Black Prince” and “Tear of Princess”. In 1946, at the Andamooka deposit, a black opal “Andamooka” with bright polychromatic iridescence was found; it was 933 ct., but after cut it became 250 ct. There was also found an opal “Nulinga Nera”, 13,375 ct., cut as an oval cabochon 205 ct. Recently, at the same deposit two findings of unique black opals have been made: “Tsarina of Night”, 1,520 ct., and “Comet of Galley”, 100x66x63 mm., 2,020 ct. Earlier, at this deposit an opal “Queen of East” was found, which was evaluated in Australian $150,000. In Australia, they treat as unique findings completely replaced with noble opal: a skeleton of a small snake, ammonite, about 15 cm. in cross-section, belemnite and shells with a piece of noble opal inside, 10x5 cm. in size.
In the AMNH N.Y. and in the Smiths. Inst., Wash., there is the largest collection of unprocessed noble opal from Australia. The size of some samples reaches 50x15 cm. in size and 1,636 ct., including: Harlequin opal – 345 and 155 ct.; black opal – 58.8 ct. Austria- \Hungary was the only supplier of noble opal till the end of the 19th cent., when the exploitation of opal deposits in Mexico and Australia has been begun. In 1775, in Slovakia, at the Dubnik deposit, an opal “Harlequin”, 12x5.7x1.1 cm. in size, 3,000 ct., was found. It is kept in the Kunst. Hist. Museum, Vienna, now. Lost without a trace black opal with fire-red play of color “Fire of Troja” was from this place. It was bought by Napoleon as a gift to his wife Josephine. Before facet it was 3,200 ct. (600 g), and after facet – about 250 ct. The largest collection of opals from the Dubnik, 366,926 pieces in general quantity and 58,645 ct. in general mass, is kept in the Nation. Museum, Budapest. In the Smiths. Inst., Wash., a unique Mexican fire opal, 143.2 ct., is exhibited, as well as a perfect opal “Aztec Eagle” from the Hope collection, 32 ct., with en engraved head of “The God of the Sun”. In 1952, in the U.S.A., at the Rainbow Ridge deposit, the biggest American transparent opal of gem-quality was extracted, 24x14 cm. in size, 16,000 car (3.2 kg.). It was called “Hodson” after the person, who found it. From the same deposit a black opal “Roebling” is 2,690 ct., 10.2x7.6x5.1 cm. in size; it is exhibited in the Smiths. Inst., Wash. After cut as an oval cabochon it is 352.2 ct. A noble opal, 11x8 cm. in size, was also found there; it is kept in the collection of the GIA now.
Synonyms. Noble opal – Eristalis, by Agricola | Oriental girasol | Ophthalmus lapis | Lechosopal (lechosos-opal), Mexican, from “leche” – milk | Mithrax, by Pliny the Elder | ~ opal: azules ~, chatoyant ~, flickering ~, Harlequin ~, after its motley color, looking like the Harlequin costume; iridescent ~, iris ~, Lighting Ridge ~, after the name deposit; matrix ~, mosaic ~, moss ~, oriental ~, peacock ~, rainbow ~ | Ophthalmus, obs. | Apocalypse stone | Celestial stone.
White opal. ~ opal: girasol ~, from Ital. “girare” – to turn and “sole” – sun; light ~, jelly-like ~, nacreous ~, water ~ | Paederos (pederot, pedros), according Pliny the Elder, from Gk. “teenager’s love”, because of its tender play of color.
Fire opal – Blitzopal, Germ. | Flimmeropal, Germ. | ~ opal: cherry ~, Mexican fire ~, red fire ~, flame ~, red flame ~, flash ~, gold ~, fiery orange ~, Simav ~, from Simav, near xapaneh Dagh, Turkey; flash star ~, sun ~ | Pyrophane, from Gk. “pyr” – fire and “phainomai” – to appear oneself | Humming bird stone, because of the similarity of their color | Fire stone | Simav stone, Turkey | Zeasit, obs.
Orange-yellow – Blackmorite, after the discovery location in Blackmore, Montana, the U.S.A. | Melichrysos, obs. | Honey opal | Lemon opal | Earthen pearls, Old Russ. | Honey-color stone, Old Russ.
Black opal – Giogetto, Ital.
Common opal – Resin agate | Alumocalcite | Fettbol, from Germ. “Fett” – fat, greasy and Gk. “bolos” | Halbopal, Germ. | Isopyre, from Gk. “isos” – the same and “pyr” – fire | Opalescent jasper | Jaspopal | ~ opal: button ~, pearly ~, pink ~, pitch ~, or resin opal and potch opal, Australian, low quality; semi ~, smoky ~, tsar’s ~ | Opalite | Pelicanite, after the Lithuanian researcher V.V. Pelican | Resinite, from Engl. “Resin” | Telkibanja stone, after the discovery location on the Telkibanya in Hungary | Tripoli stone or rotten stone, after the discovery location in Lebanon, North Africa | Vidrite.
Hyalite, from Gk. “hyalos” – glass, because of their similarity – Amiatite (amiantit) | Chamelone, after its ability to receive transparency saturating with water | Fiorite, after the discovery location near Santa Fiora, Italy | Fish-eye | Glasopal, Germ. | Ash glass | Muller’s glass, after the name of the first discoverer | Quartz glass | Hydrophane, from Gk. “hydor” – water and “phainestai” – to change oneself | jelly opal, from Engl. “jelly” | Moonstone | Oculus mundi | ~ Opal: azure ~, crystal ~, foamy ~, glass (glassy) ~, sinter ~, jelly ~, water ~ | Pealite, obs. | Pissophane, from Gk. “pissa” – pitch and “phaneros” – visual | Nacreous sinter | Pearly sinter | Siliceous sinter | Stillolith | Chameleonic stone | Changeable stone | Floating stone | Magic stone | Pearly stone | Terpizit, after the discovery location near Terpize, Saxony, Germany | Viandite.
Blue opal. ~ opal: Andean ~, after the deposit in the Andes, Peru; azure ~, Peruvian ~, from Peru; St Patrizio ~, from Peru. | Schnide, from Australia.
Iron opal – Silicious menilite | Liver opal | Nodular opal | Pech opal | Horn stone | Tin stone.
Green opal — Chloropal | Chrysopal | Allophane opal | Cristobalite opal | Prase opal | Uingvárite, after the discovery location near Uzhgorod (Hungarian name Ungvár), Ukraina.
Cacholong, from “Cache”— the name river in Kalmykia, Russia, and “cholong” – stone | Kalmyk agate | Nacreous agate | Porcelain agate | ~ opal: Chinese ~, Kalmyk ~, milk ~, nacreous ~, porcelain ~ | Porcelain opaline | Fire stone.
Opalized wood – Lithoxyl (lythoxylite) | Devil oak | Fossil opal | Wood opal | Xylonite | Xylopal.
Vegetable opal – Mascareignite, after the discovery location on the Mascarenias Iss. in the Indian Ocean | Bamboo opal | Reed opal | Tabasheer opal | Bamboo pearls | Phytolite | Tabasheer (tabaschir).
After the discovery location – Menilite, near Menile-Montone, near Paris, France | Michaelite, on the Säo Miguel Is., the Azores | Neslite, near Nesle, France | ~ opal: Andamooka ~, after the discovery location in Australia; Andean ~, rose; Chili; Brazilian ~, Chinese ~, Coober Pedy ~, after the deposit in Australia; Hungarian ~, Mexican ~, Oregon ~, after the discovery location in Oregon, the U.S.A.; Peruvian ~, rose; Queensland ~, Australia; Russian ~, from Astrakhan, Russia; White Cliffs ~, after the discovery location in New South Wales, Australia; Mexican water ~. | Quincite, after the discovery location in Quincy, France, rose.
Quality improvement. Opal is easy processed with acids and alkali, that’s why it should be cleaned only in warm water with emulators. Play of color in “dimmed” opal sometimes can be restored with saturation in oils or with long keeping in water, better in vacuum. With such methods the collection of opals in the Nation. Museum, Budapest, was saved. After the saturation with wax, white porous hydrophane becomes translucent, receives play of color and a new name – pissophane, but it is also called pyrophane. Like agate, opal, is colored with the method of sugar-acid treatment. Low quality material, which is colored black, to improve its iridescence, is called treated opal. Such opal has grained structure with iridescence only in some parts, like in French enamel, so called effect of cloisonné. Blue opal can be received as a result of the irradiation or coloring. Because of high fragility of opal, in the U.S.A. it is treated with the method of the polymer saturation, as it is done with turquoise. This method can be used to restore transparency in dehydrated opals.
Cut Gems. Opal has been known as a gemstone in India and Eastern Africa since the most ancient times. It came to Assyria, Babylon, ancient Greece and Rome from the territory of modern Slovakia. Later, through Byzantium it came to Russia. Large opal decorated the crown of the Emperor Constantine – the leader of the Holy Roman Empire. A perfect necklace from Hungarian opals, made in the 16th cent., is kept in the Nation. Museum, Budapest. Since the end of the 19th cent., opal has become very popular. It’s happened after the opening of its deposits in Australia. One of the biggest is an Australian opal “Galaxy”, which was found at the Opalville mine, in the Queensland State in 1963. Its size was 9.7x8.1x5.7 cm., and its weight after facet was 2,615 ct. In a palladium necklace of the British Queen Elisabeth II the opal “Andamooka” is set (it was described a bit earlier) among 150 brilliants. Opal was highly valued in the capital of Russia – St Petersburg; mainly the Empress Alexandra Feodorovna, who liked opals very much, created this fashion. In 1831, for the birthday of the throne heir, the Emperor Nicolas I gifted a wonderful set with opals and brilliants to his wife.
Only Mexican fire opal is faceted. Noble opals are processed in cabochons to perform play of color in them. Insets for rings, earrings, pendants are made from them and mounted mainly in gold. Sometimes, the most ornamental common opals are used for the same purposes, but they are set mainly in cheap adornments. Jewelries with opal should be treated carefully because of fragility of this stone, its ability to absorb liquids and oils, its sensitivity to high temperatures. Opal should be kept in moisture environment and sometimes it should be put in water to save its charming beauty.
Famous Stones & Jewels. The biggest among cut opals has the weight 3,749 ct., the size 139.7x101.6x41.1 mm. It is made from the opal “Galaxy”, which was extracted in Brazil. A black opal “Tsarina from Glengarry” from the Lighting Ridge deposit, Australia has the weight 1,520 ct. after cut. Other large opals were also found there: a white opal with polychromatic pattern “Pandora” – 711 ct. after cut; found in 1918 opal “Light of the World”, or “Fire Queen” with a fire iridescent spot in a green ring, 71x58x38 mm., 252 ct. after cut. In 1915, an opal “Glory of Australia” was found, after partly cut it had 225.75 ct., and also a black opal “Devon”, a cabochon 101 ct., 5x2.5 cm. in size. When the British Queen Elisabeth II visited Australia in 1954, the government of that country gifted her a necklace with an opal, 203 ct. from the Andamooka deposit. In the Smiths. Inst., Wash. there is a cabochon, 355.19 ct., which was made from the black opal “Roebling”, extracted at the Virgin Valley deposit, Nevada, the U.S.A.. In this museum there is one more cut black opal “Dark Jubilee”, 318.4 ct. In the Museum Hist. Nat., Paris, there is an opal of the King Louis XVIII, 77 ct.
Legends. Opal is a stone of false hopes. In the East, it was a symbol of loyalty and hope, happiness and truth. In ancient India, it was a stone of love, faith, compassion and creativity. As a talisman, it served a symbol of faith, happiness, hope, love and sympathy. It supports talents of its owner, gives him or a gift of prophesy, it helps to influence at the minds of other people. Even Roman legionaries, who believed in its protective forces, used it as an amulet. In medieval Venice, it supposed to be an amulet against epidemic diseases. They thought that it helped to avoid melancholy, heart and eyes illnesses. Astrologers treat opal as a stone of Water and the Moon. It is a lucky stone for those, who are born in October. It is a zodiacal stone of Cancer, Pisces and Scorpio, and black opal is a zodiacal stone only for a sign of Scorpio. Cacholong is a stone of Taurus. Opal is also a stone of those, who were born in the year of a Cat (Rabbit). It is gifted for the 14th wedding anniversary. Opal is regard as a national symbol of such countries as Slovakia, Hungary and South Wales in Australia.
Synthesis. Manufacturing of synthetic opal was patented in 1964. In 1972, in the U.S.A., the real manufacturing was opened, including a black variety. Since 1974, a Fr. firm of P. Gilson started the commercial manufacturing of synthetic harlequin opal, synthetic black opal and then synthetic Mexican opal, in which all the properties of their natural analogues were kept. In the content these opals differ from the natural ones with the percentage of water <1% and in some admixtures, that’s why we should treat them as imitations. Synthetic opals, opposite to the natural ones, usually have micro layered and columnar structure. Through the magnifier we can see mosaic patterns like “stone pavement”, “fish scales” or “lizard skin”, and in the perpendicular cut – its columnar structure. In 1979, synthetic opal was produced in Novosibirsk, Russia, at the Institute of Geology and Geophysics of the Siberian branch of the Academy of Science, and, then, in Leningrad at the enterprise “Russkie Samotsvety”; and in the end of 1980s, in Alexandrov, the Vladimir Region, at the Inst. of Synthesis of Mineral Materials. Since 1980, synthetic opal has been being produced in Japan, for example, by the firm Kyocera (Kyoto Ceramics Co.) – synthetic fire opal, and a bit later also in Australia – synthetic white opal. Since 1994, it has been being produced in China. Synthetic opal, unlike natural one, is more porous and sticky to a tongue.
Similar Gemstones & Imitations. Ammolite, labradorite, moonstone, marble onyx, nacre, chrysoprase and ivory have some similarity with some varieties of opal, but they differ from opal with optical and physical properties. Opal is very fragile, that’s why so called “compound stones” became popular in jewelry – twins and triplets with under-layer and covering from rock crystal. Sometimes, they are called “opal-triplex” or “layered opal”. Opal matrix is colored in black to strengthen its play of color. Porous opals are saturated with resins. Fine crusts of noble opal are pressed into plastic cabochons of any color. Such inset is called “encapsulated opal”. The best imitation is synthetic Gilson opal. Beautiful imitation of noble opal also is essence opal or Slocum stone, which has been being manufactured since 1964. It is made from silicon glass, enriched with sodium, with admixture of plastic sparkles, which give iridescence. Play of color in this imitation is like in opal, but less intensive; it is similar with Abalone nacre in color. More cheap imitation is milky-white glass opal, incorrectly called opalin. A new imitation is opalus; it is colorless plastic on the black background with inclusion of the thinnest foil, which gives the effect of play of color like in opal. With a microscope air bubbles are seen. One more kind of imitation can be porous sandstones and conglomerates, filled with bioorganic materials and processed with annealing. These rock materials from the Andamooka deposit, Australia, have a trade name – desert fire opal. In Japan, plastic imitation is made – neoopal, pastoral opal or neo noble opal. Similar imitation in the U.S.A. is milky-blue opalite, plastic opal from polystyrene in the shape of micro spheres, cemented in compact structure. Covered with a layer of acrylic resin, this imitation has the opal effect of play of color. An improved variety of plastic imitation is specktaculite, which has a hologram with opal play of color inside. Recently, a new opal imitation on liquid crystals is invented – sogdianerin.
Synonyms. – Opal essence | Opalus | Slocum stone, after the surname of the first discoverer G. Slocum.
Aventurine (Aventurin—Aventurine—Авантюрин), from Ital. “per avventura” – an occasion, on the similarity with aventurine glass, invented by occasion by Venetian glass blowers in the beginning 18th cent. Aventurine as a gemstone we should describe in its three varieties: rock – ornamental stone, mineral – gemstone, and artificial glass – imitation.
1. Aventurine – ornamental stone. Aventurine glance is usually a name for massive quartz, filled with inclusions of minerals, which possess sparkling luster – it gives the color to this rock. Among these minerals can be: goethite, hematite, ilmenite, chlorite, fuchsite, muscovite, rutile and others. Such aventurine can be white, rose, reddish-yellow or brownish, greenish or bluish. The most interesting ornamental varieties have golden-cherry and honey-yellow color and they are characterized with saturation of rock and regular inclusions of hematite, muscovite and rutile. These minerals give sparkling luster of the rock, so called aventurescence. Among other varieties, the most popular is green aventurine quartzite – chrysoquartz with inclusions of fuchsite, or fine-grained quartz, enriched with inclusions of chlorite. More rarely, silver-white quartzite with inclusions of fine-flaked muscovite is used. There is known also light blue-white fine-grained quartzite – eosite with brownish-red veins and spots, which contain inclusions of small cubic crystals of pyrite, which are also produce aventurescence.
Deposits. Aventurine is formed in the process of metamorphism of sedimentary rocks. In Russia, in the South Urals, near the Taganai Mt., there is the largest deposit of yellow-brown aventurine – taganaite, which has been being exploited since 1810. Similar aventurine of the best quality was extracted in the Urals, near Yekaterinburg, the village of Kosulina. Green aventurine is extracted as additional material at iron-ore deposits of Kursk magnet anomaly, in the Belgorod Region, as well as in Siberia, near Irkutsk. It is known also in Karelia and on the Kola Penin., near Kovdor – silvery quartzite, as well as in neighboring Finland. In Kazakhstan, yellow-brown aventurine is known at the deposits Zavodinskoye, Kurgasy and Kaindy. In Germany deposits of red-brown aventurine are in Bavaria; they are known also in France, near Nantes, Pays de la Loire; in Spain, Austria, Australia, on Madagascar. Among the other countries, large deposits of green aventurine are in India, where it is extracted in the region of Madras (now Chennai) under the name of Indian jade, or Indian nephrite. In the region of Jaipur, in Rajasthan a deposit of blue aventurine is exploited. In China, green aventurine is extracted, too. It is high valued they’re as imperial yu stone. In the U.S.A., green aventurine received a trade name Mariposite, or Mariposite quartz, California State. There is also red-brown aventurine quartzite in this country. In Colorado it is called gold stone, or Colorado gold stone. Significant quantities of green aventurine, as well as blue one, are sending to the world market from Brazil, from deposits of Minas Gerais.
Along with quartzite, aventurescence is observed sometimes in other quartz-containing rocks. In China, greenish-gray, rose and yellowish quartz porphyry of such kind is known in the Tibet. Because of its sparkling luster depending on inclusions of hematite flakes in quartz, it is used as ornamental stone under the trade names: astrumit, leonite, eosite or Tibet stone.
Synonyms. Avanturine | Regal jade, Germ. | Iskryak, Old. Russ. | Aventurine luster | Aventurine oligoclase | Aventurine quartz.
Golden – Gold aventurine. | Love stone | Zlatoiskr, Old. Russ.
Green —Pseudo jade | Aventurine green stone | Imperial stone | Venturine.
Cut Gems. Aventurine is easily polished; it is an ornamental stone, which is not expensive; it is used in cut stone. Transparent parts are good for cabochons. The first information about using of golden aventurine in jewelry are dated with the antique times, when it was send from India to Greece – there it was known under the names sandastros, sandares or garamantite. In ancient China, green aventurine was very popular; they made state stamps from it; it was supposed to be a holy stone. As jewelry-ornamental stone aventurine is used mainly for small cutting manufacture, because sections of rock with aventurescence have limited sizes. It is obvious in such monumental works as vases in the State Hermitage, SPb. and in the Pavlovsk Palace. The biggest of them, in the Hermitage, has the cross-section of the cup 246 cm. and the height 146 cm. A local master made it at the Yekaterinburg lapidary factory in 1842. Two small vases from green Indian aventurine with holder in the shape of elephants’ heads are in the Gatchina Palace by St Petersburg. For their geological researchers the Emperor Nicolas I gifted vases from aventurine to the German scientist A. Humboldt (1796-1859) and English geologist R.I. Murchison (1792-1871). The vase of R.I. Murchison is in the Geol. Museum of London now.
Legends. Astrologers call aventurine sunstone. As a talisman, it helps to keep good mood, spiritual activity and clearness of mind. As a love stone, it improves emotional tone, produces mutual sympathy between not very young people, awakens fantasy and stimulates unexpected deeds. In business relations it gives mutual understanding and consensus. It is not recommended for constant wearing. As an amulet, aventurine protects against nerve diseases, improves complexion. It is a lucky stone for those, who were born under the signs of Leo and Virgo, and green aventurine is especially good for those, who were born under the sign of Cancer and under the protection of the Moon.
2. Aventurine – mineral - gemstone. The name aventurine is also used for some minerals with clear aventurescence. The most often it is observed in feldspars, which is known under the names: oriental aventurine, feldspar aventurine, sunstone, oligoclase sunstone and orthoclase sunstone. Aventurescence in them appears because of the presence of inclusions of goethite and hematite in joints, which becomes a result of the dissolution of hard solutions. In Russia, in syenite pegmatites of the Potaninskoye deposit, in the South Urals, beside aventurescence in feldspar, there are also segments with the effect of moonstone. Labradorite with aventurescence has inclusions of ilmenite, sometimes magnetite or native copper. In quartz crystals it appears because of mineral powder in the zones of growing. These powders can be represented with flakes of mica, chlorite, goethite, hematite, brookite and even native gold. In the U.S.A., at the Mater Loud deposit in California, fine-dispersed native gold produces the golden tone in such quartz, which is called gold quartz, or golden aventurine quartz. Aventurine quartz with inclusions of hematite is known on the southern coast of Spain, at the Capo de Gata deposit, Prov. de Almeria, under the trade name sinopal, as well as in the U.S.A., at the uranium Marysville deposit, in Utah; and in Canada, at the deposit near Great Bear Lake. Beside quartz, other minerals with the similar effect don’t form any significant accumulations; however, they are interesting for gemologist. In the South Urals, in nephelinefeldspar pegmatites of the Ilmeny Mts., aventurine cancrinite is found. As in feldspar, aventurescence in it is produced by inclusions of hematite along the planes of joints. In aventurine beryl, aventurine vorobeyevite, aventurine aquamarine from Transbaikalia and aquamarine from Norway inclusions of hematite and goethite are placed in channels, which are oriented along crystals. In aventurine black beryl of Mozambique and Madagascar inclusions of spinel, which produce aventurescence, are linked with planes perpendicular to crystals. In aventurine zeolite from Canada this effect is connected with inclusions of small crystals of native copper.
3. Aventurine glass. The name aventurine is also used for artificial half-transparent glass with sparkling luster, which depends on numerous inclusions of small crystals. The method of its manufacturing was invented in Egypt, them it was lost, and it was reinvented in Venice. Venetian glassmakers kept the technology in secret. In 1827, it was invented anew in Germany and in 1880 in Russia. If at first only copper filings or oxides of Copper were added to this glass, later oxides of other metals were also added to receive different colors: oxides of iron – brown glass, chromium – green, cobalt – blue. Besides, aventurine-like ornamental material of rose color is manufactured – aphrodite. Aventurine glass is used as cheap material for bijoux. It differs from genuine stone in stronger transparency, less hardness, optical isotropy and properties of mineral inclusions.
Synonyms. Adventurine | Glassy aventurine | Gold aventurine glass | Gold glass | Goldfluss | Hematinon | Gold luster | Merlinite, Amer. | Gold sand | Gold stone | Love stone.
So, using of the term aventurine is reasonable only in the first case. In the other cases, it can be use as an adjective. For example: aventurine glass, aventurine analcime or aventurine labradorite and so on.