Turquoise is a hydrous copper-aluminum phosphate, CuAl6(PO4)4(OH)8·4H2O, that forms by near-surface alteration of igneous rocks rich in aluminum. (more below)
Photo courtesy Bryant Olsen of flickr under Creative Commons license
Turquoise (TUR-kwoyze) comes from the French word for Turkish, and turquoise is also sometimes called Turkey stone. Its color ranges from yellowish green to sky blue. Blue turquoise is second only to jade in value among the nontransparent gemstones. This specimen displays the botryoidal habit that turquoise commonly has. Turquoise is the state gem
of Arizona, Nevada and New Mexico, where the Native Americans revere it.
Other Diagenetic Minerals