Turquoise

Turquoise isa bluish-green mineral, obtained chiefly from Persia, where it occurs in reniform masses. It is hard, and capable of taking a high polish, being hence prized as a gem when of good colour. Chemically it consists of a hydrated phosphate of aluminium, with traces of copper and iron, to which the colour is due, and possesses a composition represented by the formula Al₄P₂O₁₁5H₂O.