Description
Blue-green phosphate. Turquoise is both a mineral and a color; as a mineral, it is an opaque, blue-to-green hydrous phosphate of copper and aluminum (chemical formula: CuAl₆(PO₄)₄(OH)₈·4H₂O), valued as a gemstone for thousands of years. As a color, “turquoise” refers to the slightly greenish blue characteristic of high-quality turquoise stones. It is a semi-precious stone, mainly found as veinlets or nuggets in alumina-rich, arid environments. The blue color is caused primarily by copper, while green hues result from iron impurities. Mohs hardness is about 5–6, making it softer than quartz.
Turquoise is rarely found in crystals but as microcrystalline aggregates or masses, sometimes intermixed with other minerals.
