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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

CLINOHUMITE


CLINOHUMITE (Klinohumit—Clinohumite— линогумит) (Des Cloizeaux, A. 1876). The name reflects its monoclinic system and on similarity of structure to humite.

Composition & Properties. Silicate – (Mg,Fe)9[(F,OH)2|(SiO4)4], subclass orthosilicates, monoclinic system. Hardness 6-6.5. Density 3.1-3.3. Glass luster. Fragile. It is found as crystals isometric in the shape, rich in edges and as grained aggregates. Transparent to translucent. Color: orange to yellow. Titanclinohumite or klinolivin with the admixtures of iron (Fe2+), titanium (Ti2+ and Ti4+) is brownish-red. For it pleochroism is typical from pale yellow to red-yellow.

Deposits. Clinohumite is formed in metasomatic transformed carbonate rocks and veins among these rocks. In Russia, in the north of the Krasnoyarsk Region, titanclinohumite is found in significant quantities at the Kugda deposit of chrysolite. Its brownish-red half-transparent crystals together with massive sepiolite are placed in pockets of chrysolite veins among olivinites. The shape of crystals is isometric to columnar, their size is not more than 5 cm. Because of cracks, the most part of crystals are available for cut in cabochons and tumbling only. From transparent segments they make faceted stones not more than 0.5 ct. In the Middle Urals, separate findings of titanclinohumite were registered at Izumrudnye kopi (Emerald Mines), and in the South Urals – at the Akhmatovskaya, Shishimskaya and Perovskitovaya mines. In Tadzhikistan, gem-quality clinohumite was discovered at the Kukh-i-Lal deposit, in the West Pamirs Mts. in 1974. There, in the zones of brecciation of forsterite skarns in loose mass of sepiolite, forming the accumulations, which are called “magals”, they found transparent clinohumite together with noble spinel. Color: from light yellow to orange-yellow with brown tone, which depends on the admixture of titanium (Ti4+) (syn. – titanolivine and red peridote). The size of crystals is not more than 3 cm. long, they are mainly with cracks; the output of rough material for faceting is small. Findings of gem-quality clinohumite are known also in other countries: in Italy – in the valley of the Ala Valley in Piedmont and at the Val Malenco deposit, Lombardy; in Spain – at the Sierra de Ronda locality, Andalucia. In the U.S.A., clinohumite was found in the Fresno Co., California; in the New York State – at the Iron Tilly Foster mine, Putnam Co.; and in the Arizona State – at the Bewell Park deposit, Apache Co. In Canada, clinohumite was found in area of Cerclend Lake, Ontario. In Brazil, of its finds are known on Jacupiranga deposit, São Paolo State.

Transparent crystals are rare, that’s why faceted stones are not more than 2-3 ct.; half-transparent material is cut in cabochons. The best material for faceting is coming from the West Pamirs Mts., Tadzhikistan.

Similarity. It looks like olivine, chondrodite and hessonite; and titanclinohumite – like andradite.

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