Turquoise

Image: Mines of the Southwest (Some rights reserved) Wikipedia: Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8ยท4H2O. It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of years owing to its unique … Continue reading Turquoise