Beautiful boulder turquoise from the '79 mines in Morristown, Arizona, U.S.A. (110x105x75 cm, 1130 kilos)

The mineral turquoise is a hydrated copper-aluminium phosphate, and its chemical formula is CuAl₆(PO₄)₄(OH)₈. The green, yellow-grey, light blue, but typically blue-green turquoise has a waxy sheen and a pale blue-white streak colour. The crystal structure is triclinic, and it breaks perfectly along one direction and well along another; however, it mostly appears in very small crystal forms, so you can't really see how it breaks in real life. The average density is 2.7, and the hardness is 5 to 6. Turquoise is not radioactive. The mineral turquoise is named after Turkey, the country through which it passed when the mineral first reached Europe; moreover, it does not occur in Turkey as far as is known. The colour turquoise is named after this mineral. Turquoise is mainly found as a secondary mineral in copper ores. The type locality is the Nishapur deposit in Iran. The mineral was also mined in the Sinai, and in Serabit el-Khadim there is a temple dedicated to the Egyptian "Lady of Turquoise" (the goddess Hathor). Turquoise is used as a semi-precious stone. The Ottoman Empire mainly exported turquoise to Persia as a precious mineral. Today, turquoise is mined in Mexico, the United States, China, and Iran. France first produced imitation turquoise in 1972, but its properties differ from those of natural varieties. However, the most commonly sold turquoise is now synthetic.