Brochantite

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Brochantite
Brochantite.jpg
General
Category Sulfate minerals
Formula
(repeating unit)
Cu4SO4(OH)6
Strunz classification 07.BB.25
Identification
Color Green, emerald green, or black
Crystal habit Prismatic crystals; acicular needle-like crystals; druse
Crystal system Monoclinic
Cleavage Perfect [100]
Fracture Conchoidal - brittle
Mohs scale hardness 3.5 - 4.0
Luster Vitreous - pearly
Streak Pale green
Diaphaneity Transparent to translucent
Specific gravity 3.97
Optical properties Biaxial (-), 2V measured: 72°
Refractive index nα = 1.728 nβ = 1.771 nγ = 1.800
Birefringence δ = 0.072
Pleochroism Weak
References [1][2][3]

Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is CuSO4·3Cu(OH)2. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it is named for its discoverer, the French geologist and mineralogist, A. J. M. Brochant de Villiers.

Crystals of brochantite can range from emerald green to black-green to blue-green, and can be acicular or prismatic. Brochantite is often associated with minerals such as malachite, azurite, and chrysocolla, and may form pseudomorphs with these minerals.

The mineral is found in a number of locations around the world, notably the southwestern United States (especially Arizona), Serifos in Greece and Chile.

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