The chemical composition of turquoise is: CuAl6(PO4)4(OH)8.5H2O!
Streak is white to pale green, luster is waxy.
Turquoise has been used as an ornamental stone for about 5,500 years. The most highly prized variety is sky blue or robin's-egg blue.
Turquoise has been mined from Serabit el Khad-im on the Sinai Peninsula since about 3400 LC; the underground workings there probably are one of the world's first hard - rock mining operations.
The bracelets of Egypt's Queen Zer contain carved Sinai turquoise and are possibly the world's oldest jewelry.
The name (French for "Turkish") refers to the trade of the material from the famous, still- active mines at Neyshabur, ran, through Turkey to Europe.
The deposits in the arid American Southwest have been worked since before the Spanish conquest; some jewelry has been found dating from perhaps AD 900.
Turquoise is rarely found in pieces larger than walnuts. It is usually polished with a low - convex, rounded surface, but it may be carved, engraved, or set in mosaics.
Because of its porosity, turquoise may retain body oils; some examples lose water and attractiveness with time.