The mineral malachite is a hydrated copper carbonate with chemical formula Cu2CO3(OH)2. It crystallizes in the monoclinic crystal system, and usually occurs in amorphous (non-crystalline) form. Malachite is often formed by precipitation from hydrothermal fluids in open spaces (voids) of rocks containing or associated with copper ores. Such precipitation takes place layer by layer, much like stalactites, forming rounded bulbs that eventually lead to a botryoidal' (grape-like) or kidney-shaped' surface. Malachite is famous for its vivid green colour and is extensively worked into trinkets and small ornaments. This specimen is from the Congolese copper-mining province Shaba, overall width is 40 cm.