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

WOLFRAMITE, GROUP: WOLFRAMITE, HUBNERITE


WOLFRAMITE (Wolframit—Wolframite—¬ольфрамит) (Wallerius, J.G. 1747). The name reflects its tungsten (wolfram) content. Ferberite (Breithaupt, A. 1863), after Rudolph Ferber of Gera, Thüringia, Germany. Hübnerite (Riotte, E.N. 1865), after Hüttenmeister Adolph Hübner, Germ. metallurgist from Freiberg. Ferberite – FeWO4 and hübnerite – MnWO4 form an isomorphic row.

Composition & Properties. Wolframite – tungstate (Fe,Mn)WO4, monoclinic system. Hardness 5-5.5. Density 7.1-7.6. Diamond luster to greasy one. Perfect cleavage in one direction. Fragile. Wolframite, which is also called wolchets (Old Russ.), is found in the form of thick-table and columnar crystals up to 20 cm. in size. They often display zonal structure. Wolframite is also represented with solid grained masses. Its color can vary from black in ferberite to red-brown in hübnerite. Non-transparent to translucent. Half-transparent to transparent crystals of hübnerite is extremely rare. They are yellowish-brown with reddish or violet tint; they look like cassiterite and sphalerite. There are their pseudomorphs on scheelite.

Deposits. Minerals of the wolframite group are widespread in pegmatites, metasomatic rocks and hydrothermal veins and on placers. In Russia, they discovered crystals of hübnerite at the Dzhida deposit in Buryatia Rep.; and in East Transbaikalia, crystals of wolframite up to 15 cm. length were found at the deposits Bukuka and Belukhinskoye, in the region of Nerchinsk and others. In the Primorskiy Region crystals of hübnerite were found at the Arsenyevskoye deposit and wolframite – at the Zabytoye deposit. In Yakutia, beautiful crystals of wolframite were found at the Alyaskitovoye deposit, in the basin of the Indigirka River, by Ust’-Niora. Similar findings were made on the Chukchi Penin., at the Iul’tin deposit. In Central Kazakhstan, crystals of wolframite up to 16x16 cm. in size were extracted at the deposits Aqshataü and Quara Oba; and in the Balkhash Region – at the Kounrad deposit.

In Norway, a crystal of ferberite 25 cm. long at the Modum deposit, Buskerud Region, is found. In Germany, tabular crystals up to 10 cm. occur in ore deposits of the Erzgebirge, Saxony. In Czech Rep., crystals of wolframite up to 20 cm at the Cinovec mine are known; also large crystals at Krupka and Horní Slavkov, Bohemia (historical region). Crystals of the same size were found in Romania, at the Baia Sprie deposit. In Portugal crystals of wolframite up to 15 cm. and of ferberite 30 cm. at Panasqueira were extracted. In Egypt, occur crystals up to 10 cm. in quartz-cassiterite veins from Abü Dabbad, Arabian Desert. In Rwanda, ferberite pseudomorphs on scheelite crystals up to 5 cm. at the Gifurwe mine are found. In China, crystals of wolframite up to 7 cm. in size came to the market from the Guangdong and Gansu Prov. In Japan, at the Otome mine, they discovered ferberite pseudomorphs on scheelite. In Canada, at the Mt. Pleasant tin-tungsten mine, they extracted crystals of wolframite up to 10x15 cm. in size. In the U.S.A., at the Long Hill deposit, Connecticut, they found wolframite pseudomorphs on scheelite; and at several deposits in Colorado – crystals of hübnerite. In Peru, at the Pasto Bueno mine, Pagliaska Prov., occurred translucent crystals of red hübnerite up to 15 cm. long, which were faceted for collection purposes. Besides, at the Huallapon mine, Ankash Dept., hübnerite crystals up to 25 cm. long were found. In Bolivia, fine tabular crystals ferberite up to 8 cm. occur in the Llallagua Dist., Potosí.

Rare transparent crystals are faceted, non-transparent ones are cut in cabochons sometimes.

Search