What is turquoise?
Turquoise is a hydrated copper aluminium phosphate mineral. Its ideal formula is CuAl6(PO4)4(OH)8 * 4H2O, although natural material can be chemically variable and may contain related minerals from the turquoise group.
Mineralogy and appearance
Turquoise crystallises in the triclinic system and is usually opaque, fine-grained, massive, globular or vein-forming rather than made of large visible crystals. Colour ranges from bright blue and sky blue through blue-green to pale green and green-grey. Matrix may appear as dark or brown veining. The attached structure image uses an exact turquoise host model from COD 5000101.
Formation and localities
Turquoise is a secondary mineral of oxidised copper deposits. It forms where copper-bearing fluids interact with aluminium- and phosphate-rich material, often in arid or semi-arid environments. Historic and modern material is known from Iran, the United States, China, Egypt, Chile and other regions.
Use in mosaic
Turquoise supplies saturated blue and blue-green accents in stone mosaic. Natural matrix and colour variation can be part of the design, while stabilization or other treatment should be recorded separately when known.
