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Turquoise
Gemstone
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Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its... Wikipedia
Associated month: December
Hardness (Mohs hardness scale): 5 – 6
Chemical formula: CuAl₆(PO₄)₄(OH)₈ • 4H₂O
Birefringence: +0.040
Cleavage: Perfect on, good on, but cleavage rarely seen
Crystal class: Pinacoidal (1); (same H–M symbol)