File:Cuprosklodowskite (Musonoi Mine, Kolwezi, Zaire) 2.jpg

English: Cuprosklodowskite from Zaire, Africa. (Robert Lauf collection)

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 5500 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 silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4.

Cuprosklodowskite is a scarce hydrous copper uranyl hydroxy-silicate mineral, Cu(UO2)2(SiO3OH)2·6H2O. It has a nonmetallic luster, a greenish color, is 4 on the Mohs Hardness Scale, forms elongated, acicular (needle-like) crystals, and is radioactive. Cuprosklodowskite 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 silica, cuprosklodowskite can form.

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 cuprosklodowskite:

www.mindat.org/gallery.php?min=1191