Brochantite
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Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is Cu₄SO₄(OH)₆. Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it was named by Armand Lévy for his fellow Frenchman, geologist and... Wikipedia
Color: Green, emerald green, or black
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Prismatic crystals; acicular needle-like crystals; druse
Crystal system: Monoclinic
Formula (repeating unit): Cu4SO4(OH)6
Fracture: Conchoidal
IMA symbol: Bct