Cu2CO3OH2

Cu2CO3OH2 is commonly referred to as basic copper carbonate, with the conventional chemical formula Cu2CO3(OH)2. In mineralogy and older literature it is sometimes written as Cu2CO3OH2; the standard representation for the compound is Cu2CO3(OH)2. The compound occurs as the mineral malachite when found in nature and is a hydrated copper carbonate hydroxide.

Overview and occurrence

Basic copper carbonate forms in the secondary oxidation zones of copper ore deposits, where it precipitates from copper-containing solutions. It is widely distributed worldwide, often occurring alongside other secondary copper minerals such as azurite. In nature it commonly appears as botryoidal, stalagmite-like, or layered masses and can also form crystal clusters. Malachite, the mineral form, is prized for its characteristic vivid green color.

Structure and properties

The compound consists of copper(II) ions coordinated to carbonate groups and hydroxide, creating a basic copper carbonate lattice. It is typically opaque with a green color that ranges from light to dark. The hardness on the Mohs scale is about 3.5 to 4, and it has a relatively high density compared with many other minerals. Chemically, it is a hydrated copper carbonate hydroxide, and heating causes decomposition with release of water and carbon dioxide, leaving copper oxide.

Uses and safety

Historically, malachite was used as a green pigment and as a decorative stone in jewelry and carvings. Today it is mainly collected as a mineral specimen or mined as a minor copper ore. Copper compounds can be hazardous; handling powder or dust requires care to avoid inhalation or skin contact, and prolonged exposure should be mitigated.

See also

Malachite, azurite, basic copper carbonate pigments.