mineral
Turquoise
Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)
Hardness: 5–6 Mohs; Color: Sky blue, blue-green, or apple green; Luster: Waxy to sub-vitreous; Crystal Structure: Triclinic (usually cryptocrystalline); Cleavage: None; Specific Gravity: 2.6–2.9.
- Hardness
- 5–6 Mohs
- Color
- Sky blue, blue-green, or apple green
- Luster
- Waxy to sub-vitreous
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Physical properties
Hardness: 5–6 Mohs; Color: Sky blue, blue-green, or apple green; Luster: Waxy to sub-vitreous; Crystal Structure: Triclinic (usually cryptocrystalline); Cleavage: None; Specific Gravity: 2.6–2.9.
Formation & geological history
Formed as a secondary mineral by the percolation of meteoric acidic solutions during the weathering and oxidation of pre-existing minerals. It is typically found in arid climates within volcanic rocks or sedimentary environments rich in aluminum and copper.
Uses & applications
Primarily used as an ornamental stone and gemstone in jewelry, such as rings, necklaces, and turquoise inlay work. It has deep cultural significance in Native American and Persian traditions.
Geological facts
Turquoise was one of the first gemstones ever mined. The earliest known mines were in the Sinai Peninsula of Egypt around 3000 BCE. Its name comes from the French 'turquois', meaning 'Turkish', because it first reached Europe via Turkey.
Field identification & locations
Identification includes checking for 'matrix' (veins of host rock), its waxy luster, and specific gravity. Common locations include Iran, the Southwestern United States (Arizona, Nevada), China, and Egypt. Collectors should watch for 'stabilized' or dyed howlite substitutes.
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