Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia



DIOPSIDE (Diopsid—Diopside—ƒиопсид) (d’Andrada J.B., 1800), from Gk. “dis” – double and “opsis” – view, because two views can be taken of its prismatic form.

Composition & Properties. CaMg[Si2O6]. Silicate, subclass chain silicate. Monoclinic system. Hardness 5.5-6.5. Density 3.2-3.4. Glass luster. Cleavage in one direction. Separation in two direction. Diopside is a mineral of the group of pyroxenes, it forms the row of constant miscibility with hedenbergite with the gradual decrease of the magnesium-content and increase of iron. To diopsides as they are, we should classify a member of this row – salit, and also intermediate in content augite-diopside, aegirine-diopside and fassaite. Diopside is found as short-columnar crystals, their radial-rayed aggregates and grained masses. The maximum size of crystals is 1 m. The variety of color of diopside is a reason to classify it as a polychromatic gemstone. The dispersion of color is, sometimes, zonal or sectorial. Diopside as itself is light bluish-green and yellow-green because of chromophors iron (Fe2+and Fe3+), and salit and coccolite are yellow-green because of Fe2+ to golden-yellow because of Fe3+; chromdiopside or chrome-diopside is emerald-green, green because of chromium (Cr3+), violan, or mangan-diopside can be purple-violet to light blue because of manganese (Mn3+ and Mn2+), anthocroite, schefferit and jeffersonite are light rose and yellowish to brownish because of Mn2+; lavrovite is grass-green because of vanadium (V3+). Transparent to translucent. In cabochons diopside, sometimes, displays asterism with four or six-radial star because of inclusions of magnetite, and the effect of cat’s-eye because of tube inclusions. Diopside with well-developed separation and iridescence has its own name – diallage, or malacolite. Diopside and its varieties in gem-quality crystals are classified as nonexpensive gemstones. Besides, they are rock-forming minerals of different ornamental stones.

Deposits. Diopside is widespread. It is formed in magmatic rocks and their pegmatites, during metamorphism and contact metasomatism. In Russia, in the Middle Urals, at the Bazhenovskoye deposit near the city of Asbest, they found crystals of diopside, available for cutting. In the Gusevogorskiy pyroxenite massif, rose diopside is represented with veins, up to 1 cm. thick. In the South Urals, at the Akhmatovskaya mine near Zlatoust, they found gem-quality diopside in crystals up to 5 cm. long with zonal color from colorless to green. At the Lebyazhinskoye deposit, diopside is bottle-green, in crystals up to 10 cm.; at the Jremjevskaya mine – up to 20 cm. In Pribaikalia, in the fold Uluntui, at the Slyudyanka deposit they extracted grayish-blue crystals of baikalite, up to 10 cm. in size, with transparent sectors. There, at the open-pit Pereval, they discovered chromium-vanadium diopside – lavrovite of apple-green hue, 4-8 cm. in size, as inclusions in marbles. In Yakutia, at the deposits Leglier and Emel’dzhak, on Aldan, they registered findings of crystals of diopside up to 30 cm. long. In Polar Yakutia, at the Titovskoye deposit polychromatic crystals of salits of zonal coloring were found: from light rose in the base, yellow and light green to rose on the tips. At the Kovdor deposit in the Murmansk Region, they extracted iris diopside with iridescence in large blocks as additional material; it was enough good as an ornamental stone.

In Kyrgyzstan, at the Kanskoye deposit, South Fergana, they discovered gem-quality diopside and diopside cat’s-eye; and in pyroxenites of the Alaiskiy Range (Alai Mts.) aegirine-diopside was discovered in the form of transparent, emerald-green crystals up to 1.5 cm. In Finland, superb green prismatic crystals chrome-diopside up to 10 cm. occur in copper ore deposits as at Vuonos, near Outokumpu. In Austria, available for faceting diopsides were found near Heiligenblut, Carinthia, in the end of the 19th cent. There, in the form of druses in cavities among serpentinous rocks they found large crystals of bottle-green color – Heiligenblut crystals, or saualpite. Near Zillertal, in alpine veins, they extracted transparent green diopside up to 30 cm. long and white diopside cat’s-eye. In Switzerland, such alpine veins with diopside are known near Zermatt, Valais canton. In Italy, alpine veins with diopside were discovered at the Brosso deposit, in the Ala Valley; and near Traversella, Peidmont, they discovered gem-quality emerald-green fassaite. There, near San Marcel, Aosta, for the first time violet-blue violan was found. In Romania, at the Ocna de Fier deposit, they described the finding of schefferit in the form of long-prismatic crystals of dark brown to black color. There were also found crystals of diopside with alteration of color from grayish-green to red-gray. At the Dognecea deposit, Caraš -Severin Dept., prismatic crystals of diopside, up to 15 cm. long, were equal in their content to ferrosalite enriched with manganese. At the Bâita Bihor deposit diopside is represented with flattened prismatic crystals of yellow hue, up to 10-12 cm. in size.

On Madagascar, gem-quality green diopside is found at several deposits in the southern parts of the island. At one of them, near Ampandrandara, available for processing crystals of diopside reached 20x17x14 cm. in size. At the Itrongay deposit, Toleara Prov., green diopside in cavities of orthoclase-microcline pegmatites; also in crystals up to 13 cm. at Beraketa, near Bekily, was extracted. In Tanzania, gem-quality light green crystals diopside up to 5 cm. occurs at Merelani Hills deposit, near Arusha. In South Africa, crystal of diopside 1 m. long at the Palabora mine, East. Transvaal, were found. In Kenya, light green diopside cat’s-eye in Kwale region, were found. In Western Australia, 250 km. east from Carnarvon, the deposit of transparent dark green diopside was discovered, from this material they made faceted stones up to 100 ct. In Myanmar, near Mogok, in kimberlitic pipes thy found crystals of diopside with light bluish tone; there also diopside cat’s-eye was found. On Sri Lanka, at placers by Ratnapura they extract yellow-brown and red-brown gem-quality diopside, as well as transparent bright green diopside with asterism. In India, at the Nammakal deposit, Tamil Nädu, diopside cat’s-eye is extracted together with transparent green crystals and black star diopside, which display four and six-radial stars. In the Jammu and Kashmir State (disputed area), at the Chamachhu deposit transparent diopside crystals length up to 9 cm. were found. At the Hunza River, they discovered diopside cat’s-eye. In China, a deposit with similar rough material was discovered in the Kunglung Ridge, in the Xinjiang-Uygur Autonomous Territory. In Afghanistan, they extract gem-quality light blue diopside in transparent crystals and translucent grained aggregates. It is known under the trade name aovine. Besides, diopside available for faceting was discovered in Iran.

In Canada, in the Ontario Prov., gem-quality bottle-green and reddish-brown crystals of diopside up to 14 cm. they extract. In the Québec Prov. dark green shiny crystals up to 12 cm. at Huddersfield, and light brown crystals up to 14 cm. at the Orford mine were extracted; also yellow-brown one at the deposits Lorel, Orford Nickel and Trois Riviere. In the U.S.A., at the De Kalb deposit, of New York State, they found unique in quality transparent crystals of colorless diopside – dekalbite, from which they made faceted stones up to 38 ct. Such crystal 10 cm. in cross-section, is exhibited in the AMNH, N.Y. In New Jersey, reddish brown crystals up to 6 cm. of schefferit and up to 25 cm. of jeffersonite occur in deposits at Franklin and Sterling Hill, Sussex Co. available for faceting green-black and chocolate-brown jeffersonite with the content of MnO around 8% and ZnO – 7%. In Brazil, at the Malacacheta deposit, in Minas Gerais State they extracted gem-quality diopside and diopside cat’s-eye; and at the Córrego Setuba deposit transparent crystals of diopside reached 30 cm. long.

Chromdiopside is the most precious faceting variety of pyroxenes. In 1968, in Russia, in the south of Yakutia, 30 km. north from Aldan they discovered the Inagli deposit, and in 1973, they opened its exploitation. By the early of 1998, they have extracted 32 tons of crystalline rough materials. Chrome-diopside has there the trade name siberlite. The deposit is situated in a massif of ultra basic rocks and it is linked with diopside-orthoclase-mica metasomatic rock. Their thickness varies from 5 to 115 m. Resources of chrome-diopside in crystal rough material were 28 tons on the 01.01.2002, including the material available for faceting – 780 kg. and for cut in cabochons – 640 kg. Its crystals are from yellowish-green to dark green. They reach 50 cm. in cross-section, however, because of cracks fragments available for faceting are not more than 3 cm. Less bright faceting material comes to the market from Kenya. In Finland, at the Mekkivaara deposit, near Outokumpu, they find the biggest isolations of emerald-green chrome-diopside. In Rep. of South Africa, chrome-diopside and chrome-diopside cat’s-eye were discovered in diamond pipes at the Kimberley deposit. Besides, findings of chrome-diopside are known on Madagascar, in New Zealand and Australia. Chrome-diopside is located in Cuba – at the Moa deposit, in Mexico – in the Chihuahua State, in Japan – Akita Pref.

Ornamental rocks. Diopside jade. – Diopside exists in the content of jadeite and similar ornamental stones of the jades type. These are massive rocks almost completely composed with grained aggregate of different colored diopside. In Russia, in the West Sayan Mts., in the Ijimskiy massif of the Rep. of Tyva, they discovered such rock of the type of carcaro with the trade name diopside jade. It is almost monomineral diopsidite composed with twisted-fibrous diopside. It is white, light yellow and pale green in color. In several regions of East Siberia, they found massive blue diopside with transfers to green hue as a rock-forming mineral. Such rocks are formed mainly at the contact metasomatism in the bodes of skarn; and they are of interest for processing. They are known at the East Sayan Mts., in the upper reaches of the Kazyr River, in skarn of the Zapevalikhinskiy gabbroid massif. In North. Pribaikalia, rocks with blue diopside are developed in skarn of the Yoko-Dovyrenskiy massif as zones up to 30 cm. thick; and in West. Pribaikalia – at the contact zone of the Tazheranskiy alkali massif. In the Kemerovo Region, monomineral accumulations of blue diopside up to 15 cm. are found in skarned limestone of the Bis Tag deposit at the Kuznetskiy Alatau. There, in the region of Minusinsk, Khakassia, they discovered ornamental serpentinites diopsidite-bistagite composed with white diopside. In the south of the Krasnoyarsk Region, in Gornaya Shoriya, they discovered the Balakhchinskoye deposit of blue diopside. In Yakutia it was discovered in skarn of the Mukhal’skiy alkali massif; on Aldan – in skarn of the Murun alkali massif and on the Vitimskoye Plateau. In the region of Slyudyanka, in marbles and in quartz, interlayers of apple-green chrome-vanadium lavrovite exists as fine-grained accumulations. It is also found in interlayers of quartz-diopside rocks, up to 1.5 m. thick. In East Siberia, at the Inagli deposit, of chrome-diopside as an ornamental stone it is extracted additionally emerald-green chrome-diopside rock with black spots of serpentinous dunite, called incorrectly leopardite. On the Kola Penin., at the Pechenga deposit there is ornamental pyroxenite with crystals of white diopside on black background. In pre-Columbian America, diopside jade was known in Mexico as an ornamental stone – tuxtlite, or mayaite. This massive rock of pea-green hue is composed with diopside jadeite. In the north-west of China, in the Xinjiang-Uygur Autonomous Territory, they use plagioclase-diopside diorite as an ornamental stone under the trade name Tekesscian green jade. In Japan, on Central Hokkaidö, Hidaka jade is popular; it is an ornamental stone composed with chrome-diopside with admixture of uvarovite, chromite and pectolite. In Italy, Piedmont, near Traversella, green to colorless nephrite-like diopside jade is called traversellit, or carcaro. In Great Britain, near the western shore of Scotland, on the small Tayri Is. they find diopside as inclusions in ornamental rose marble – Tayranian marble.

Synonyms. Alalite, after the discovery location in the valley of Ala, Piedmont, Italy | Chrome-augite | Baikalite (baicalit), after the discovery location near Baikal Lake, Russia | Bistagite, after the discovery location in the Bis-Tag mine, near Minusinsk, the Krasnoyarsk Region, Russia | Vanadium bronzite | Coccolite, from Gk. “coccos” – a grain, after the shape of accumulations | White coccolite | Diallage, from Gk. “diallage” – to alternate, because of separations | ~ diopside: ferrous ~, mangan ~, Indian sapphire black star ~, vanadium ~. | Erlanite, after the discovery location in the Erla deposit, Saxony, Germany | Fassaite, after the discovery location in the valley of Faso, South. Tyrol, Italy | Jeffersonite, after the Amer. President T. Jefferson | Lavrovite (lavroffite), after the Russ. mineralogist Lavrov, the name discredited by IMA | Malacolite – from Gk. “malacos” – soft, because it is more soft than found with it plagioclase | White malacolite | Mussite (massite), after the discovery location in the valley of Mussa, Piedmont, Italy | Sahlit, after the discovery location near Sahla, Sweden | Augite radiated stone, obs. | Corsican verde | Violan, from Ital. “viola” – violet, after its color.

Chromdiopside – Siberian emerald, Russia | Siberlit (sibirlit).

Diopside jade – Diopsidite, after the content | Hidaka jade, Jap.| Mayaite (maeaite), after the discovery location in the tombs of Maya, Mexico | Tuxtlite, after the statuettes by Maya made from this material – “tuxli”.

Cut Gems. In jewelry diopside is used mainly in the faceted form. In this case, the table facet of the stone is oriented along the side facet of a crystal of diopside, because under the perpendicular orientation to the long axis, undesirable yellowish-brown hue is displayed. Stones with optical effects and ornamental diopside rocks are cut in cabochons, processed for beads or used in for stone-carving. In the collection of the Smiths. Inst., Wash., a faceted chrome-diopside from Finland is exhibited, 1.6 ct., as well as a yellow diopside from Italy, 6.8 ct., a green one from Madagascar, 19.2 ct. In the AMNH., N.Y., there is a green diopside from the U.S.A., of New York State, 38 ct. In the Smiths. Inst., Wash., there is a cabochon from diopside cat’s-eye from India, 24.1 ct. and a star diopside, 133 ct.

Similarity. It looks like other pyroxenes, vesuvianite, hiddenite, emerald, moldavites and chrysolite.