Descloizite
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Descloizite is a rare mineral species consisting of basic lead and zinc vanadate, Template:Chem2, crystallizing in the orthorhombic crystal system and isomorphous with olivenite.[1] Appreciable gallium and germanium may also be incorporated into the crystal structure.
The color is deep cherry-red to brown or black, and the crystals are transparent or translucent with a greasy lustre; the streak is orange-yellow to brown; specific gravity 5.9 to 6.2; hardness 31/2. A variety known as cuprodescloizite is dull green in color; it contains a considerable amount of copper replacing zinc and some arsenic replacing vanadium.[1] There is also an arsenate analogue called arsendescloizite.[2]
Discovery and occurrence
It was discovered in the Sierra de Córdoba deposit in Córdoba, Argentina, in 1854 and named in honor of the French mineralogist Alfred Des Cloizeaux (1817–1897).[3] It occurs as small prismatic or pyramidal crystals, usually forming drusy crusts and stalactitic aggregates; also as fibrous encrusting masses with a mammillary surface.[1]
Descloizite occurs in oxidised portions of veins of lead ores in association with pyromorphite, vanadinite, wulfenite, mottramite, mimetite and cerussite.[4]
The Otavi ("O-tarvi") Mountainland of northern Namibia was once considered home to the greatest vanadium deposits in the world, including those at Berg Aukas ("OW-cuss"), Abenab ("UB-en-ub"), Baltika ("BUL-tika") and Uitsab ("ATE-sub").[5] Descloizite and mottramite were the main ore minerals in each of these deposits, which are now exhausted. Other localities are the Sierra de Cordoba in Argentina; Lake Valley in Sierra County, New Mexico; Arizona; Phoenixville in Pennsylvania and Obir, Carinthia Austria.
See also
References
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- ↑ a b c One or more of the preceding sentences incorporates text from a publication now in the public domain: Script error: No such module "template wrapper".
- ↑ Arsendescloizite on Mindat.org
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- ↑ Boni et al., 2007, Genesis of vanadium ores in the Otavi Mountainland, Namibia. Economic Geology v.102 p.441-469.
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