Azurite
Azurite is a deep-blue copper carbonate mineral with the formula Cu3(CO3)2(OH)2. It is formed by the weathering of copper ore deposits. Azurite is known for its intense color and is often associated with malachite, another copper carbonate mineral.
Properties:
- Color: Deep azure blue to dark blue.
- Luster: Vitreous to silky.
- Streak: Light blue.
- Hardness: 3.5 to 4 on the Mohs scale.
- Crystal System: Monoclinic.
- Cleavage: Perfect on [010], good on [100].
- Fracture: Conchoidal.
- Specific Gravity: 3.7 to 3.9.
- Solubility: Soluble in acids.
Occurrence:
Azurite is found worldwide in oxidized zones of copper deposits. Notable occurrences include:
- Arizona, USA
- France
- Namibia
- Mexico
- Morocco
Uses:
- Ornamental Stone: Azurite is used as a gemstone and for ornamental purposes, often in combination with malachite.
- Pigment: Historically, azurite was ground into a pigment for use in paints and dyes. Over time, it can alter to malachite.
- Mineral Specimens: Well-formed azurite crystals are highly prized by mineral collectors.
Distinguishing Features:
Azurite can be distinguished from other blue minerals by its characteristic deep blue color, its effervescence in dilute hydrochloric acid, and its association with copper deposits. It is softer than most blue gemstones, such as sapphire or spinel.
Alteration:
Azurite is unstable in open air and slowly alters to malachite, a green copper carbonate. This process is sometimes visible on specimens as a green coating or alteration throughout the azurite.