mineral
Turquoise
Hydrated phosphate of copper and aluminium (CuAl6(PO4)4(OH)8·4H2O)
Hardness: 5-6 Mohs; Color: Sky blue to apple green; Luster: Waxy to subvitreous; Crystal Structure: Triclinic (usually massive); Specific Gravity: 2.6-2.9
- Hardness
- 5-6 Mohs
- Color
- Sky blue to apple green
- Luster
- Waxy to subvitreous
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Physical properties
Hardness: 5-6 Mohs; Color: Sky blue to apple green; Luster: Waxy to subvitreous; Crystal Structure: Triclinic (usually massive); 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; typically found in arid regions within volcanic rocks or sedimentary phosphate deposits.
Uses & applications
Primarily used as a gemstone in jewelry (cabochons, beads, inlays) and for decorative carvings or ornamental objects.
Geological facts
Turquoise is one of the oldest known gemstones, used by Ancient Egyptians and Native Americans for over 3,000 years. Its name comes from the French 'turquois' meaning Turkish, as it first reached Europe via Turkey.
Field identification & locations
Identified by its distinctive blue-green hue and waxy luster. Common in the Southwestern US (Arizona, Nevada) and Iran. Watch for 'Howlite' dyed to look like turquoise; real turquoise is harder and color does not rub off with acetone.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock