Rock Identifier
Turquoise (Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)) — mineral
mineral

Turquoise

Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)

Hardness: 5-6 (Mohs scale); Color: Sky blue, blue-green, or apple green; Luster: Waxy to sub-vitreous; Crystal Structure: Triclinic (usually cryptocrystalline); Cleavage: Perfect (rarely seen in massive specimens); Specific Gravity: 2.6-2.9.

Hardness
5-6 (Mohs scale)
Color
Sky blue, blue-green, or apple green
Luster
Waxy to sub-vitreous
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Physical properties

Hardness: 5-6 (Mohs scale); Color: Sky blue, blue-green, or apple green; Luster: Waxy to sub-vitreous; Crystal Structure: Triclinic (usually cryptocrystalline); Cleavage: Perfect (rarely seen in massive specimens); Specific Gravity: 2.6-2.9.

Formation & geological history

Formed by the percolation of acidic aqueous solutions during the weathering and oxidation of pre-existing minerals. It is a secondary mineral found in arid regions, often occurring as veins or crusts in altered volcanic rocks.

Uses & applications

Predominantly used as a gemstone in jewelry (cabochons, beads, inlays) and for ornamental carvings. Historically used for amulets and protection stones.

Geological facts

Turquoise is one of the oldest known gemstones, used by the Egyptians in the First Dynasty. It is often associated with 'Robin Egg Blue' and can change color over time due to exposure to oils, light, or chemical changes.

Field identification & locations

Identify by its unique sky-blue to green color and waxy appearance. In the field, look for it in arid climates near copper deposits (e.g., Southwestern USA, Iran). Collectors should check for stabilization (resins), as many stones are treated to improve durability.

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