English: Torbernite from Zaire. (Wayne State University collection, Detroit, Michigan, USA)

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The phosphate minerals have one or more phosphate anions (PO4-3).

Torbernite and metatorbernite are scarce hydrous copper uranyl phosphate minerals. They have a nonmetallic luster, deep green color, light green streak, are fairly soft (H=2.5), typically have tabular crystals forming closely-packed clusters, and are radioactive. These minerals are principally valued as collector specimens and not as ore minerals of uranium. Torbernite is Cu(UO2)2(PO4)2·10H2O. Metatorbernite is Cu(UO2)2(PO4)2·8H2O - it forms by partial dehydration of torbernite. Torbernite is a secondary uranium mineral that forms by alteration of uraninite (or other primary U minerals) in an oxidizing environment. The original U+4 ions in uraninite get oxidized into U+6 and usually become incorporated into uranyl ions, (UO2)+2. In the presence of water, copper, and phosphorus, torbernite can form. In dry air, torbernite alters to metatorbernite.

Locality: Musonoi Mine, west of the town of Kolwezi, southern Katanga Province, southern Zaire ("D.R. Congo") (locality info. at www.mindat.org/loc-4322.html )

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Photo gallery of torbernite: www.mindat.org/gallery.php?min=3997

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Photo gallery of metatorbernite:

www.mindat.org/gallery.php?min=2689