Azurite and malachite on iron oxide gossan from Arizona, USA. (~5.0 centimeters across at its widest)

Blue = azurite Green = malachite Reddish-brown = gossan matrix

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 5400 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 carbonate minerals all contain one or more carbonate (CO3-2) anions.

Malachite and azurite are attractive, richly colored copper hydroxy-carbonate minerals. Malachite has a nice green color - its formula is Cu2CO3(OH)2. Azurite has a dark, rich blue color - its formula, Cu3(CO3)2(OH)2, is very close to malachite. The blue color of azurite is from Cu+, while the green color of malachite is from Cu+2. Azurite & malachite almost invariably occur together, and are telling indicators of copper in the field, even in very small quantities. Blue azurite tends to crystallize first, and can convert to green malachite. Some azurite-malachite specimens are solid enough to be cut and polished as semi-precious stone.

Locality: Morenci Mine, western Greenlee County, southeastern Arizona, USA

Photo gallery of azurite: <a href="http://www.mindat.org/gallery.php?min=447" rel="nofollow">www.mindat.org/gallery.php?min=447</a>

Photo gallery of malachite: