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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

WULFENITE


WULFENITE (Wulfenit—Wulfenite—¬ульфенит) (Haidinger, W. 1845), after Franz Xavier Wülfen (1728-1805), Austrian mineralogist; author of a monograph on the lead ores of the discovery location, Bleiberg, Carintia, Austria.

Composition & Properties. Molibdate – Pb[MoO4], tetragonal system. Hardness 3. Density 6.5-7.0. Diamond luster or greasy one. Cleavage in one direction. Fragile. Color: orange-red, red, brown, olive-green, greenish-brown, more rarely light blue because of the admixture of molybdenum (Mo4+) and colorless. Transparent to translucent. Wulfenite sometimes looks like baryte. It is a rare mineral found in the form of isometric and table crystals and grained masses.

Deposits. It is widespread in the oxidation zone of lead-ore deposits. In Kazakhstan, wulfenite is known at the Alabuga deposit, by Karkalinsk, in the form of red crystals up to 1 cm. in cross-section, as well as at the Eastern Kounrad deposit in the Balkhash Region; and in the south of Kazakhstan – at the Suleyman Say deposit and others. In Uzbekistan, there is the Sidzhak deposit in the Ugamskiy Ridge, to the northeast from Toshkent (Tashkent), with orange-red crystals up to 4 cm. In North Tadzhikistan, crystals of wulfenite up to 2 cm. were found at the deposits Darbaza and Kansay, to the north from Khujand, in Karamazar Ridge. In Austria, at the Bleiberg mine, Carinthia, its yellow and brown-yellow crystals up to 3 cm. were discovered (so called carinthite or Carinthian lead spar). In Morocco, wonderful crystals of wulfenite up to 12 cm. at the Bou Azzer deposit, near Quartzzeit, and at Mibladen mine, near Midlet, were extracted. They were also found at the Jabel Mahseur deposit, near Oujda; and at the Zelija mine, near Touissit. In Namibia, variously colored wulfenite crystals up to 8 cm. at the Tsumeb deposit are known. Here, also greenish-light blue vanadium-containing wulfenite eosite are found. In Congo (Brazzaville), at the M’Fuati deposit, occur its pale green crystals and orange up to 10x10x5 cm.. In Iran, at the deposits Shakh Mille and Shakh Kharboze, near Anaräk, wulfenite crystals up to 3 cm. were found. In the U.S.A., in Arizona, gem-quality crystals orange-yellow wulfenite at the Rowley mine, Maricopa Co.; and crystals up to 12 cm. at the Hilltop mine, near Portal; also larges crystals clusters at the Defiance mine, near Gleeson. In Pennsylvania, at the Phoenixville deposit, they extracted yellow and reddish crystals – yellow lead ore. In Mexico, in the Sonora state, yellow crystals of wulfenite up to 13 cm. were extracted at the Cerro Prieto (San Francisco) mine, near Magdalena. In the Chihuahua State, at the mines Ahumada and Los Lamentos the size of wulfenite crystals was not more than 6 cm. They made faceted gems up to 9 ct. from that material.

Treatment. Because of its low hardness, wulfenite is processed for collection purposes only. They made faceted gems up to 50 ct. from it or doublets with covering. In the Museum of Calgary, Canada, there is a faceted yellow stone in 15.25 ct. from the Tsumeb deposit and a red one in 9.44 ct. from Arizona. In one of private collections there is a yellow stone from the Tsumeb deposit in 54 ct.

Synthesis. There are data on producing of synthetic wulfenite, which is used in jewelry.

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