mineral

Turquoise

Hydrated phosphate of copper and aluminium [CuAl6(PO4)4(OH)8·4H2O]

Hardness: 5-6 (Mohs scale), Color: Sky blue to blue-green, Luster: Waxy to subvitreous, Crystal structure: Triclinic (usually microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.9

Identified March 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the percolation of acidic aqueous solutions during the weathering and oxidation of pre-existing minerals. It is a secondary mineral usually found in arid regions within volcanic rocks or sedimentary deposits rich in phosphorus and aluminum.

Uses & applications

Primarily used in jewelry (cabochons, beads, and inlay) and decorative arts. Historically used in talismans and religious artifacts.

Geological facts

Turquoise is one of the oldest gemstones in history; it was mined by the Ancient Egyptians as early as 3000 BCE. Its color depends on the ratio of copper (more blue) to iron or aluminum (more green).

Field identification & locations

Identify by its unique 'Robin's Egg' blue color and often the presence of a dark brown or black 'matrix' (remnants of host rock). Common locations include Iran, the Southwestern United States (Arizona, Nevada), and China. Collectors should look for natural, untreated stones versus 'reconstituted' or dyed magnesite/howlite.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral

Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

mineral