Turquoise

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

Rock Type: mineral

Turquoise

Physical Properties

Hardness: 5-6 Mohs; Color: Sky blue to apple green; Luster: Waxy to subvitreous; Crystal structure: Triclinic (usually cryptocrystalline); Cleavage: Perfect (rarely seen); Specific gravity: 2.6-2.9

Formation & Geological History

Secondary mineral formed in the oxidation zones of copper deposits by the percolation of meteoric water through aluminous rock in arid environments.

Uses & Applications

Primarily used in jewelry (cabochons, beads, and inlay) and as a highly prized collector specimen; historically used for amulets and decorative ornaments.

Geological Facts

One of the first gemstones ever mined, turquoise was highly valued by the Egyptians as early as 3000 BCE and held deep spiritual significance for Native American tribes in the Southwest US.

Field Identification & Locations

Identify by its distinctive blue-green color and waxy luster; often contains dark matrix veins (limonite or manganese oxide). Commonly found in Iran, Southwestern USA, China, and Egypt.

Identified on: 5/18/2026

Mode: Standard