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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

STIBIOTANTALITE


STIBIOTANTALITE (Stibio-Tantalit—Stibiotantalite——тибиотанталит) (Goyder, F.A. 1893). The name reflects its antimony (Gk. “stibi”) composition and similarity to tantalite. Oxide – SbTaO4, orthorhombic system. Hardness 5-5.5. Density 6.2-7.9. Pitch luster to diamond one. Cleavage in two directions. Fragile. Stibiotantalite is a rare mineral, which is found in the form of columnar or flattened crystals and grained masses. Color: brown to yellowish-brown, reddish-yellow to red-brownish, greenish. The dispersion of color is zonal. Non-transparent to translucent, in rare cases transparent. It is found in granite pegmatites and on placers. In Russia, stibiotantalite crystals were discovered in Rep. of Tyva, in spodumene pegmatites of the Kara Adyr deposit. In East Kazakhstan, they were discovered at the Ungursay deposit, near Ust’-Kamenogorsk. In other countries, stibiotantalite was found in Sweden, at the Varuträsk deposit; in Czech Rep. – in pegmatites of Dobrá Voda, Moravia. The most representative deposits of this mineral are known in Mozambique, in the Alto Ligonha region. Here, at the Muiane deposit, crystals of stibiotantalite with transparent segments up to 12x10 cm. are found; and at the Ribaué deposit, the weight of the biggest crystals reached 4 kg. In Zimbabwe, stibiotantalite at the deposits Mutoko (Mtoko) and Bikita was found. In India, in the Jammu and Kashmir State (disputed area), it is extracted from pegmatites of Stak Nala, Gilgit area. In Western Australia, crystals of stibiotantalite in pegmatites of the Greenbushes deposit, near Bridgetown, were discovered. In the U.S.A., red-brown, brownish yellow crystals up to 5 cm., available for faceting, at the Himalaya mine, Mesa Grande Co., California, were extracted; also as crystals fragments up to 5x3.5 cm. from the Brown Derby pegmatite, Gunnison Co., Colorado. In Canada, they are known at the Bernic Lake deposit. Besides, there are data on their findings on placers of Brazil.

Stibiotantalite as a rough material for faceting comes mainly from Mozambique and California, the U.S.A. From transparent segments of crystals they make faceted gems of reddish-brown to straw-yellow color, up to 10 ct.

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