Azurite, basic copper carbonate,
Formula Cu3(CO3)2(OH)2.

Crystal system: Monoclinic.
Hardness: 3.5 to 4
Density: 3.7 to 3.9 gms/cm3
Colour: Blue.
Streak: Light blue.

Azurite is a popular mineral in collections because of its attractive blue colour. It is widespread as a mineral though less common than malachite [ Cu2CO3(OH)2] with which it is usually found. Azurite and malachite are significant copper ores and are also used for ornament. The finest crystalline specimens of azurite come from Chessy in France, Touissit in Morocco and Tsumeb in Namibia.

The provenance of the azurite specimen shown in the picture is unknown. It was selected because of its deep blue, highly lustrous crystals.

Deep blue Azurite crystals of unknown provenance