chrysocolla

chrysocolla, a silicate mineral, hydrated copper silicate, CuSiO₃·2H₂O, formed as a decomposition product of copper minerals in most copper mines, especially in arid regions. It occurs as crusts or masses in the upper parts of copper ore veins where the copper minerals have been altered by water containing dissolved silica. Specimens with a fine green or bluish green colour may be used as ornamental stones. For detailed physical properties, see silicate mineral (table).

The term chrysocolla was applied by Theophrastus and other ancient writers to various materials used in soldering gold.