Antlerite

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Antlerite

General
Category Mineral
Chemical formula Copper sulfate hydroxide, Cu3(SO4)(OH)4
Identification
Color Bright green, through darker greens to black
Crystal habit tabular and acicular or fibrous. Also found as reniform, massive or granular specimens
Crystal system Orthorhombic bipyramidal
Cleavage Unidirectional
Fracture Uneven
Mohs Scale hardness 3.5
Refractive index 1.72-1.78
Pleochroism x: yellowish green
y: bluish green
z: bluish green
Streak Pale green
Specific gravity ~3.9

Antlerite is a greenish hydrous copper sulfate mineral, with the formula Cu3(SO4)(OH)4. It occurs in tabular, acicular, or fibrous crystals with a vitreous luster. Originally believed to be a rare mineral, antlerite was found to be the primary ore of the oxidised zones in several copper mines across the world, including the Chuquicamata mine in Chile, and the Antler mine in Arizona, USA from which it takes its name. It is chemically and optically similar in many respects to other copper minerals such as malachite and brochantite, though it can be distinguished from the former by a lack of effervescence in hydrochloric acid.