Turquoise Gems and Jewelry
Like a pearl, turquoise is an opaque gemstone. It is a blue to green (sometimes yellow) mineral consisting of hydrated copper and aluminum phosphate. Its chemical formula is CuAl6(PO4)4(OH)8·4H2O. Turquoise belongs to the triclinic crystal system and is a relatively soft gem, with a Mohs hardness of 5 to 6. Citation
