carbonate salts of copper. Normal copper carbonate has not been isolated yet. Copper carbonate (basic) occurs in nature as the emerald green mineral malachite, CuCO3 · Cu(OH)2, and the sky blue mineral azurite, 2CuCOa. Cu(OH)2. The basic carbonate CuCO3 - Cu(OH)2 · 0.5H2O is obtained by the action of Na2CO3 on CuSO4 in an aqueous solution; upon heating, the carbonate is converted into malachite.
Copper carbonates are unstable and at temperatures above 200°C break down into CuO, CO2, and H2O. They are insoluble in water but can be dissolved in ammonia in the presence of ammonia salts. Azurite is used as a pigment; it is also used in pyrotechnics, metallurgy, and other industries. Both azurite and malachite are used in the fashioning of decorative objects and jewelry.