Turquoise is a blue-green mineral (hydrous phosphate of copper and aluminum) that has been prized as a gemstone for millennia. Turquoise jewelry adorned elites in ancient Persia, Egypt, Mesopotamia, China, and Mesoamerica. Sources of turquoise include Iran, the Sinai peninsula, and the southwestern US. Web resources here, here and here.

Mosaic mask. Turquoise, cedro wood, conch shell, mother of pearl, gilding, cinnabar. Mixtec–Mexica. Ca. 1400–1521. British Museum, London.