mineral
Turquoise
Hydrated copper aluminum phosphate (CuAl6(PO4)4(OH)8·4H2O)
Hardness: 5-6 Mohs; Color: sky-blue to blue-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 to blue-green
- Luster
- waxy to sub-vitreous
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Physical properties
Hardness: 5-6 Mohs; Color: sky-blue to blue-green; Luster: waxy to sub-vitreous; Crystal structure: Triclinic (usually cryptocrystalline); Cleavage: none; Specific Gravity: 2.6-2.9
Formation & geological history
Forms as a secondary mineral in the oxidation zone of copper deposits, typically through the infiltration of meteoric acidic water through weathered surface rocks containing aluminum and phosphorus.
Uses & applications
Primarily used as a gemstone for jewelry and ornamental carvings. It has been used for thousands of years in amulets and decorative mosaics.
Geological facts
Turquoise is one of the oldest known gemstones, used by the ancient Egyptians and Persians. Its sky-blue color comes from copper, while green hues are caused by iron or chromium impurities.
Field identification & locations
Identify in the field by its distinct color, lack of cleavage, and occurrence in arid regions within copper-rich volcanic rocks. Watch for 'matrix' (vein markings) which can be black, brown, or gold.
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