Turquoise

Formula: CuAl6(PO4)4(OH)8.4H2O

Origin of name: from French for Turkish

 

Crystal system: triclinic

Crystal class: -1

Twinning:

Unit cell: a = 7.49 Å, b = 9.95 Å, c = 7.69 Å, a = 111.7°, b = 115.4°, g = 69.4°

 

Colour: blue to green, greenish blue

Diaphaneity: 

Luster: vitreous, waxy, dull

Habit: crystals short prismatic, small, rare, massive, dense, cryptocrystalline to fine-granular, concretionary, stalactitic

Hardness: 5 to 6

Specific gravity: 2.6 to 2.8

Cleavage: 2; {001} perfect, {010} good

Tenacity: conchoidal to smooth

Streak: 

 

Synonyms/varieties: agaphite, callaina, henwoodite, johnite

 

Comments: series with chalcosiderite and with planerite

 

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