Chemical composition -- Hydrated copper aluminum phosphate.
Color-- Blue, green, blue-green.
Optics -- R.I. 1.62.
Durability -- Hardness 5-6.
Crystal structure -- Triclinic(massive).
Specific Gravity-- 2.6-2.9.
Sources -- Iran (Persia), Tibet, China, Egypt, southwestern U.S.
Turquoise has been widely used in Native American jewelry, inlays, and carvings. Much of the mass-market material has been permeated with resin and other substances to seal porous material and to improve color. Very fine, untreated material is fairly scarce.