Turquoise is an opaque mineral that occurs in beautiful shades of blue, bluish green, green, and yellowish green. It has been treasured as a gemstone for thousands of years. Isolated from one another, the ancient people of Africa, Asia, South America and North America independently made turquoise one of their preferred materials for producing gemstones, inlay, and small sculptures.

Chemically, turquoise is a hydrous phosphate of copper and aluminum (CuAl₆(PO₄)₄(OH)₈·4H₂O). Its only important use is in the manufacture of jewelry and ornamental objects. However, in that use it is extremely popular – so popular that the English language uses the word “turquoise” as the name of a slightly greenish blue color that is typical for high-quality turquoise.

Very few minerals have a color that is so well known, so characteristic, and so impressive that the name of the mineral becomes so commonly used. Only three other minerals – gold, silver, and copper – have a color that is used more often in common language than turquoise.