s
Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

OBSIDIAN


OBSIDIAN group (Obsidian—Obsidiane—ќбсидиан) (Theophrastus, 320 B.C.) from Gk. “opsianos” – vision, or show, because black obsidian, especially that from Ethiopia, was used for manufacturing of mirrors. According another version, Lat “opsianus” after the tribe name Obsius on the territory of modern Ethiopia. Pliny the Elder supposed, there was a Roman man named Obsius, who as if had taken a stone from Ethiopia. Here also rocks close to obsidian are described – natural glasses: perlite, basaltic glass, rhyolite, vitrophyre, porphyry and porphyrite.

Composition & Properties. Rock with the composition of SiO2 up to 75%, H2O<1%. Hardness 5-5.5. Density 2.3-2.6. Glass luster to resin one, silk one. Very fragile. Amorphous volcanic glass of effusive genesis. The content of obsidian is alternating, from such one of rhyolite to basaltic glass, or basaltic obsidian. Obsidian is found in nature as flows of glassy lava in the regions of volcanic eruption. The structure of rock is massive, the texture is homogeneous, spotty, often stripped or brecciated. Non-transparent, translucent to transparent. Color: gray, green, reddish-brown, black. Black variety of obsidian in the U.S.A. has the trade names Nevada black diamond, mountain jet, and stripped, black-red one – red mountain wood, brown one with gray stripes like mahogany – mahogany mountain wood. Brecciated obsidian of chocolate-brownish hue is known as persian. A rare variety is green pseudochrysolite, or Montana jade; more rare is almost transparent aquamarine obsidian from Mexico and dark violet strombolite. Translucent bluish-gray obsidian with silky play of color is known as muslin stone, or lynx sapphire. It is called also Tokay lynx  sapphire, Hungarian obsidian, and because of mistake in the translation – Tokay lux sapphire. Smoky translucent variety of obsidian has the trade name Nevada topaz, and colorless transparent one – mountain glass, hyalite or glassy agate. Especially evaluated is obsidian, overfull with the smallest gas-liquid inclusions, which produce iridescence because of their fine-layer disposition, and the effect of cat’s-eye in cabochons. In transparent differences, there is opalescence because of small glass globules, which were formed in the process of liquation of lava. From there on, such varieties were formed as silver obsidian, gold obsidian, iris obsidian, chatoyant obsidian, and rainbow obsidian. The last one is also called midnight lace and peacock tail. Peculiar properties of the texture are the base of such varieties as web obsidian, banding or onyx obsidian, Iceland agate or spotty royal agate. Grayish-white inclusions of cristobalite on the black background resembling snowflakes gave the name to snowflake obsidian. It is also called flocculent, flowering and porphyrite obsidian. The presence of powder inclusions of magnetite is the reason of the black color of obsidian.

Deposits. Obsidian is widespread as a product of volcanic eruptions in the regions of young volcanism. In Russia, its deposits are situated in the Northern Caucasus – Chegem and Zayukovskoye. In Transbaikalia, there is the Mukhtor Talinskoye deposit. In the Khabarovsk Region, there are two small deposits of obsidian in the Obluchenskiy Dist. – Pad’ Fedoseikha and Radde. On the Kamchatka Penin., on the western slope of the Sredinnyi Ridge, there is the Itkovayam deposit with red as sealing wax obsidian; and to the west from Petropavlovsk-Kamchatskiy there is the Nachikinskoye deposit with resources of perlite.

In Transcaucasia, obsidian is extracted in South Azerbaijan, at the Kechaldak deposit. In Armenia, at the Arteni deposit, in the T’alin Dist., by the railway station of the same name, they extract black obsidian with brown tones of landscape and polychromatic varieties. One more Guiymushskoye deposit, near Geghashen (Razdan), is characterized with black and spotty obsidian. At the Akunskoye and Gutansarskoye deposits, in the Abovyan Dist., there are different varieties of obsidian, including golden-yellow and ash-gray ones. In Georgia, at the Parvan deposit, on the bank of Parvany Lake, they find brown-black landscape obsidian, as well as silver-black one. In Tadzhikistan, there is the Tashcesken obsidian deposit, Khujand (form. Leninabad) Dist. In Kazakhstan, in the of Alma Ata Region, they researched the Arkalyk deposit with black vitrophyre – an analogue of glassy syenite.

In other countries, obsidian is extracted in Iceland from where it is taken under the trade name Iceland agate. In Finland, near Sordaval, they discovered a variety of obsidian – sordawalite, or wichtisit. In Italy, ornamental obsidian is known on the Lipari Iss. In Hungary, brown-black translucent obsidian with the silky play of color is extracted at the deposits Tokaj and Palkhasi, where it is called Tokay lux sapphire. In Africa obsidian is extracted mainly in Ethiopia. In South-Eastern Asia, deposits of obsidian are known first of all in Japan an Indonesia. In Japan, deposits of obsidian are situated on the Hokkaidö Is. In America, obsidian has been known to aboriginal population since the pre-Columbian ages. They made arrow-heads from it. In the U.S.A., in Utah, at the Coyote Springs deposit, Millard Co., they extract snowflake, or flocculent obsidian, in which “flakes” are represented with cristobalite. In Oregon, snowflake obsidian was discovered in the Cascade Mts., and at the Glass Butts deposit they extracted polychromatic rainbow obsidian, or midnight lace. Snowflake obsidian comes to the market also from California – Coso Hot Springs deposit, and others. In New Mexico, such variety of obsidian is popular as Apache tears. On Hawaii and in Nevada, they extract iris obsidian and flowering obsidian. In Mexico, deposits of golden obsidian and iris obsidian, or iris opal are situated in the states of Jalisko, Hidalgo and Querétaro, where they extracted also obsidian cat’s-eye. In the San Luis Potocí State, rainbow obsidian displays colored stripes and iridescence because of its fine structure. It has the trade name Maya obsidian, after the ancient peoples of Maya; Aztecs treated it as a magic stone. Beside obsidian, in Mexico, they use volcanic glass – ramosite, from the Ramos locality, in San Luis Potocí, for adornments. Besides, in Guatemala deposits of obsidian the La Joya mine are known; in Nicaragua and in Ecuador. In Peru and Colombia, volcanic glasses were taken falsely for tektites earlier, that are why they were called americanites, but in reality they were obsidian.

Synonyms. Anthrakion, by Theophrastus (372-287 B.C.) | False chrysolite | Water chrysolite | Iris glass, syn. iris opal | Isophyr, from Gk. “isos” – the same, after the structure | Itali, local name among Aztecs, Mexico | Macusanite, after the discovery location in Peru; earlier it was classified as tektitesamericanites | Mountain mahogany | Montana jade, after the discovery location in the Yellowstone Park, Montana, the U.S.A. | Rétinit, Fr., chocolate color | Divine stone or magic stone, the Aztec name “teotetl” | Marathon stone, local name, the U.S.A. | Obsidian onyx | Opal onyx, obs. | Persian, after the discovery location in Iran (form. Persia) | Bottle stone | Strombolite, after the Stromboli Is., the group of Lipari Iss., Italy | Vanakite, local name after Van Lake, Armenia.

Quality improvement. Because of the low price, the stone is not improved. A rare example is discoloration for faceting – Nevada diamond.

Treatment. Obsidian has been known to people and used by them since the Paleolithic Age. They made knives, arrow-heads from it as well as adornments and amulets. The most ancient findings are dated to 10 thousands years ago. In the British Museum, London, there are obsidian beads made in the 5th millennium B.C. In Ancient Egypt, they cut vessels for incenses from obsidian. In Lisbon, a head of the Pharaoh of the 12th dynasty Senusert III is kept, which was cut from obsidian. Pliny the Elder also mentioned an obsidian bust of the Emperor Augustus; and Augustus himself gifted four elephants from obsidian to a temple of the goddess of Concordia. In the pre-Columbian America, Aztecs and Mayas manufactured mirrors, magic balls and figures of gods from it; they called obsidian divine stone. In the Museum Hist. Nat., Paris, there is the obsidian “Inca Mirror”. It was among the treasures, sent by Cortez to Spain in 1552. In the AMNH, N.Y., there is also an obsidian mirror, 33.7x30 cm. in size. Transparent varieties of obsidian from the deposits of the U.S.A. – Glass Boots, Oregon and Superior, Arkansas – are used for faceting. Obsidian is used in different countries of the world for small stone-carving work of art. In 1914, the Ural stone-cutter A.K. Denisov-Ural’skiy in a serial of allegoric figures symbolizes the countries, which took part in the World War I, represented Great Britain as a sea-lion from obsidian. In the Armory Museum Kreml., Moscow, there is a figure of a horse from obsidian by the firm of K. Fabergé, made by M.E. Pryakhin.

Legends. According ancient legends, obsidian is a protective stone. It warns against improper deeds, takes heart away from unfaithfulness. As a talisman, it helps to its owner to be more precise. It is a stone of caution. Astrologers connect it with the planet of Pluto and recommend it to those who were born under the signs of Leo, Sagittarius and Capricorn. In Mexico, obsidian is a national symbol of country.

Similarity and imitations. Obsidian looks like some tektites, jet, smoky quartz and morione. Imitations are not typical and usually are represented with glass.

Perlite, from Germ. “perl” – pearls, because of its spherical loosening. A variety of volcanic glass. Content – SiO2 up to 75%, H2O 5-6%. Hardness 5-5.5. Density 1.3-1.6. Perlite differs from obsidian with its concentric-shelly texture. This specific of the texture gave it the name pearly stone. Under weathering of perlite transparent sphaerolites are accumulated, which are usually processed with the method of tumbling. The size of sphaerolites is not more than a few cm. in diameter. In Russia, in Transbaikalia, there are the Mukhtor Talinskoye and Zakulitinskoye deposits of perlite. Yellow perlite in Nerchinsk Dist. is called kulibinite. In the Khabarovsk Region, near Okhotsk, on the Sukhoy Marekan River, they extracted almost colorless, smoky or reddish-brown perlite – marekanite with easy detached glassy sphaerolites. In the Primorskiy Region, they exploit the Chuguevskoye deposit of perlite and zeolites. In the Ukraine, near the railway station of Muzhiyevo in Zakarpats’ka Region, there is the Pelican deposit of perlite. In Armenia, there are the Aragatskoye and Jraberskoye deposits. In Iceland, green-black variety of perlite – fluolite is popular. In the U.S.A., in Arizona, near Superior, they exploit a deposit of white, glassy perlite, which was formed as a result of transformation of obsidian. Perlite of brownish-black color with resin luster they call pitch stone. Its porphyry-like variety is stigmite. Sphaerolites of perlite in the U.S.A. have the trade name apache tears. They were found near Los Alamos, New Mexico, and also in Mexico, Jalisko State; and in Costa Rica, near Palmar Sur.

Synonyms. Fluolite, from Lat. “fluo” – flow, after its texture | Pearly volcanic glass | Kulibinite, after the Russian mining engineer A. Kulibin | Porphyrite obsidian | Peanut onyx, because of its sphaerolites texture | Pissite, from Gk. “pissa” – resin, pitch | Pitchstone, from Germ. “pech” – resin, pitch | Retinite, from Gk. “retine” – resin | Porphyrite pitch stone | Tabona, local name on the Tenerife Is., the Canary Iss., Spain.

Basaltic glass, after the similarity with glass. Rock with the content of SiO2 up to 50%. Hardness 6. Density 2.7-3. Glass luster. Amorphous. A product of underwater basalt lava flow. The main varieties of basaltic glass are sideromelane and tachylyt. Sideromelane is a water-free, transparent variety of basaltic glass of light green color. Tachylite, from Gk. “tachys” – fast and “litos” – stone, because of fast crystallization, is a non-transparent, dark brownish rock, often with admixtures of chlorite and clay minerals. Hyalomelan is its porphyry-like variety. Under aquation of basalts in their cavities, spherical isolations are formed like amygdales; they are represented with light green chlorite-like palagonit, called after the discovery location on Sicily, Italy, which ancient name was Palagonia. In Georgia, in the Zhavakhet Plateau, there are deposits of basaltic glass. In Nicaragua, there is the El Vosce deposit of ornamental palagonit. On Hawaii and in Czech Rep. they extract jewelry-ornamental tachylite. These rocks are extracted in significant volumes and are used as ornamental stones. In Australia, in Northern Queensland, on the Flinders River brown up to black basaltic glass was quarry.

Rhyolite, from Gk. “rheo” – flow, after its texture, it is recommended instead of the syn. liparite. Magmatic rock with the content of SiO2 about 73%. Hardness 5-5.5. Density 2.6. Rhyolite is an effusive analogue of granite It is characterized with its stripped fluidal texture – a consequence of lava flow, and porphyrite structure because of inclusions of quartz or cristobalite and feldspars. Ornamental varieties of this rock, like landscape rhyolite, are used as ornamental stones. Here, we also describe other ornamental rocks: hälleflinta, porphyrys, porphyrites and volcanic breccia. In Russia, rhyolite are found in the Northern Caucasus, in the region of Mineral’nye Vody, in the mountains Mashuk, Beshtau and Zheleznaya. Another region of their wide developing is Kamchatka. In the Amur Territory, on the southern slope of the Stanovoy Ridge, there is the well-known Belyi Utës deposit of ornamental fluidal rhyolites. In the Ukraine, ornamental rhyolite are known in Zakarpats’ka Region, and also on Crimea, in the Karadag Mt. They are exploited also in Armenia and Azerbaijan. In Australia, Australian rhyolite green up to brown with bluish inclusions chlorite. In the U.S.A., ornamental silicification rhyolite – creolite is known in the Shasta, at San Bernardino Co, California. In New Mexico, a pattern variety of red-brown to orange-yellow ribbon rhyolite is known as an ornamental stone under the trade name elixirite. One more variety of ornamental rhyolite is found in Pennsylvania, near South Mountain. It is greenish-gray with reddish tone copper rhyolite, containing inclusions of native copper, azurite, malachite, cuprite and epidote. In Mexico, is ornamental chrysanthemium rhyolite, or starred agate, brown color with star-shaped inclusions, and also orbicular rhyolite, or leopard jasper is popular, with red vitreous “eyes” 2-4 cm. in diameter on the blue to whitish background. Similar is almond-shaped rhyolite from Germany with amygdales of agate and chalcedony, more than 1 cm. in cross-section. In Australia, in the area of Mt. Hay, Queensland, they described spheroidal rhyolite under the name tropical wood jasper. Sphaerolites of chalcedony are placed in greenish-brown matrix with admixture of brownish epidote and green chlorite.

Liparitic tuffs. Acid lavas are very tight, and in the process of their eruption large masses of pyroclastic material are formed, that’s why along with liparite its tuffs are known. Such liparitic tuffs are found in Russia, in the Northern Caucasus, in the basins of the rivers Baxan, Nal’chik, Chegem deposit. This massive gray and rose rock can be used as ornamental and coating stone. Hälleflinta is a micro-grained quartz-feldspar hornfels of the class of metamorphic rocks, formed in the process of contact metamorphism of quatz porphyrys or rhyolites. Ornamental varieties are used as an ornamental stone like hornstones and jaspers. The sample if hälleflinta of the iron-ore deposit Kostomuksha in Karelia, Russia. Porphyrys and porphyrites are magmatic rocks with cryptocrystalline main mass and porphyry insets of feldspars. Porphyrys are classified as alkali rocks like syenites, and porphyrites – as basic rocks of diorite content. These names are used only with the general name of the rock. Because of massive texture and bright color they are often called jaspers. They are well-polished and beautiful in color, that’s why some varieties of these rocks can be used as coating and sometimes even as ornamental stones. Many ornamental jasperoids are transformed porphyrys.

In Russia, in the Northern Caucasus, in the Krasnodar Region, they extract jasper-like porphyrys, liparites and tuffs at the Urushtenskoye and Kutanskoye deposits. In the Urals, deposits of porphyrys and porphyrites are traced along the whole the eastern slope. In the Middle Urals, near Neviansk, there is the Ayatskoye deposit of ornamental gray-green Ayatsk porphyrites, also called Ayatsk jasper. In the region of Nizhniy Tagil, there is the Belyakovskoye deposit of diorite porphyrite of greenish color with red and white insets of plagioclase, and near Rezh – the Rezhskoye deposit of similar rocks. Since 1829, in Bashkortostan, near Talkass Lake, they have known the Talkasskoye deposit of red porphyrys. It was also called Tanalykskoye or Isyanovskoye, because of the location near the village of Isyanova. These ornamental rocks are similar with red antique porphyry from Jebel Deccan locality, Egypt. Red color of this rock depends on admixture of manganese-containing epidotewithamite. In the State Hermitage, SPb., there are vases from Tanalyk porphyry and Altai porphyry. The Aushkul’skoye deposit of diorite porphyrites is situated in the Uchaly Dist., Bashkortostan. In the Altai Korgonskiy porphyry has been popular since the ancient times; many vases, cups and standard lamps exhibited in the State Hermitage, SPb. had been made from it. Its deposit has been known since 1786. It is located in the Ust’-Kansk Dist., near the junction of the rivers Korgon and Charysh. It is massive gray-violet rock with insets of quartz and feldspar and small amygdales of chalcedony. With the presence of amygdales up to 10 cm. this rock is called kopeychataya jasper, or cone porphyry. With the dominance of brownish-red tone it is called sealing wax jasper. Popular Altai porphyry is called chocolate porphyry or violet porphyry, because of its even and bright color; its varieties are Bolsherechenskiy and Loktevskiy porphyry, as well as multicolored porphyry and labradorite porphyry, also called Chayr-Kumir jasper, or Chayr-Kumir breccia. In this region of Altai they found different types of porphyrys, including dark green porphyry by Zmeinogorsk, black porphyry of the Mokrushinskaya Mt. and pauper grained quartz-diorite – Kolyvanskaya jasper. Ornamental porphyrys and porphyrites are found in Buryatia Rep. and in the Primorskiy Region. Such is the Novodevitsa deposit with andesitic porphyrite in the Hankaiskiy Dist. There are sealing-wax-red and massive greenish-gray rocks with white insets of plagioclase and dark ones of hornblende.

In the Ukraine, in the Zhitomir Region, there is the Mikhailovskoye deposit of diabase porphyrite – volhynite. It is massive greenish-gray rock with porphyry isolations of labradorite of the middle size – 1-2 cm. wide. In 1876, there, near Ovruch, they discovered the first deposit of red jasper, represented with quartz porphyrys. Jasperoids of the similar origin are known on Crimea, on the slopes of the ancient volcano Kara Dag. These are silicification rocks of yellow, brocade and lilac-red color, so called Pheodosiya jasper and green trass. In Armenia, Geghashen (Razdan) Dist., there is the Tezhsarskoye deposit of ornamental epileucitic porphyry. It is gray with greenish tone rock with big insets of epileucite, feldspar and dark colored mineral. In Tadzhikistan, in the Khazhokhaskiy area, Khujand (form. Leninabad) Dist., they discovered a deposit of ornamental porphyrys. It is massive dark gray to black rock with irregular oriented insets of labradorite up to 3 cm. in size.

Quartz porphyry is one of the analogues of rhyolite and it is used as an ornamental stone because of its decorative properties. Quartz-porphyrys are widespread in Russia, in the Middle Urals, Altai; and in Kazakhstan and countries of Middle Asia. In Kazakhstan, they use red Karasayskiy porphyry as an ornamental stone. Similar deposits are in other countries of the world. In the U.S.A., in California, they extract quartz porphyry – leopardite, resembling leopard skin because of uneven coloring with hydroxides of iron and manganese. In Canada, near Superior Lake, they extract flower stone, which is ornamental black porphyry with white plates of plagioclase, resembling flowers.

Volcanic breccia as an ornamental stone is known in Russia in Karelia, to the north from Petrozavodsk, at the Solomenskoye deposit. It is gray-green to dark gray massive rock composed with acute fragments, mainly with porphyrite, with small amygdales of chalcedony in cement. Another sample in the Urals is porphyrite breccia from Bashkortostan. It is massive rock of exquisite shaped, light colored fragments, cemented with cryptocrystalline basic mass of green hue. In Buryatia Rep., there are deposits of ornamental volcanic lavabreccia. One of them is the Ducharskoye deposit, where lavabreccia consists of acute fragments of liparite, cemented with gray volcanic glass. In Tadzhikistan, at the Yangiken deposit, to the north from the Cherukh Dairon mine, Khujand Dist., they discovered resources of ornamental tuff breccia. It is massive rock with fragments of yellow, brownish and reddish rocks are cemented with light beige mass. The size of fragments is not more than 2 cm. The rock can be polished to the mirror state.

Synonyms. Liparite, after the discovery location on the Lipari Is. in the Tyrrhenian Sea, Italy – Elixirite, local Amer. name, which sows at the volcanic origin | Tropical wood jasper, Queensland, Australia | Eye rhyolite, from Mexico | Green rhyolite | Spherical rhyolite | Striate rhyolite | Leopard skin.

Hälleflinta, from Swedish “hälle” – rock and “flinte” – chert, after the similarity.

Chalcedonic trass, from Ital. “terasso” – deck, after the shape of finding – Chernomorite | Ayvasovskiy stone | Landscape stone.

Porphyry, from Gk. “porphyryos” – red, because antique porphyry was usually of red hue; the similar origin is for the name porphyrite – Bagrovnik, local, Ural. | Altai porphyry | Red porphyry | Panther stone.

 

 

Search