Turquoise JewelryWhere the name comes from: French pierre turquoise - "Stone from Turkey", while there was a significant amount of trading the stone that went on in Turkey, it originated from nearby countries and regions.
Where the stones come from: Iran, Sinai, USA, sometimes it is a by-product from large copper mines.
Chemistry: A hydrous phosphate of copper and aluminium, CuAl6(PO4)4(OH)8.4H2O
Colors: Sky blue through paler blue to blue-green, the bluer forms are more sought after and more valuable.
...and another thing: Turquoise is rather sensitive to physical damage and also can be changed by cosmetics, heat, oils (including those in the skin, so it should be touched as little as possible) and even bright lights.