turquoise science definition

A blue to bluish-green or yellowish-green triclinic mineral that occurs in reniform (kidney-shaped) masses with surfaces shaped like a bunch of grapes, especially in aluminum-rich igneous rocks such as trachyte. In its polished blue form it is prized as a gem. Chemical formula: CuAl₆(PO₄)₄(OH)₈·5H₂O