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 5900 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.

The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2). All other silicates have silica + impurities. Many silicates have a significant percentage of aluminum (the aluminosilicates).

Chrysocolla is a distinctively colored copper hydroxy-silicate mineral - CuSiO4(OH) (also given as Cu2-xAlx(H2-xSi2O5)(OH)4·nH2O). It is usually bluish to bluish-green to greenish colored. It does not form crystals, only amorphous masses or botryoidal crusts. Some crystalline-looking occurrences of chrysocolla are pseudomorphs from previous minerals. Chrysocolla is a secondary mineral associated with other copper-bearing minerals such as cuprite and malachite.

Locality: Blue Jay Mine, Leadore Mining District, northeastern flanks of the Lemhi Range, southeastern Lemhi County, Idaho, USA (vicinity of 44° 36' 43 North latitude, 113° 33' 29 West longitude)

Photo gallery of chrysocolla: