mineral
Turquoise
Hydrated phosphate of copper and aluminum, CuAl6(PO4)4(OH)8·4H2O
Hardness: 5-6 (Mohs scale); Color: sky-blue to blue-green; Luster: waxy to sub-vitreous; Crystal Structure: Triclinic; Specific Gravity: 2.6-2.9
- Hardness
- 5-6 (Mohs scale)
- Color
- sky-blue to blue-green
- Luster
- waxy to sub-vitreous
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Physical properties
Hardness: 5-6 (Mohs scale); Color: sky-blue to blue-green; Luster: waxy to sub-vitreous; Crystal Structure: Triclinic; Specific Gravity: 2.6-2.9
Formation & geological history
A secondary mineral formed in the alteration zones of copper deposits, typically in arid or semi-arid environments where groundwater percolates through aluminous rock in the presence of copper phosphorus.
Uses & applications
Primarily used as a gemstone in jewelry (cabochons, beads, inlays) and as an ornamental stone in many cultures.
Geological facts
Turquoise is one of the oldest known gemstones and has been mined for over 6,000 years, notably by ancient Egyptians and Persians. Its name comes from the French 'turquois' meaning 'Turkish', as it was originally brought to Europe via Turkey.
Field identification & locations
Identified by its unique robin's egg blue or greenish-blue color and waxy appearance. Often found as vein fillings or nodules in arid regions like the Southwestern US, Iran, and China. Collectors look for color purity and absence of 'matrix' (host rock).
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