Chalcophyllite
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Chalcophyllite is a rare secondary copper arsenate mineral occurring in the oxidized zones of some arsenic-bearing copper deposits. It was first described from material collected in Germany. At one time chalcophyllite from Wheal Tamar in Cornwall,... Wikipedia
Color: Blue-green to emerald-green
Crystal class: Rhomboedral (3); H-M symbol: (3)
Crystal habit: Crystals platy and six-sided, also as rosettes, drusy, foliated or massive
Crystal system: Trigonal
Optical properties: Uniaxial (−)
Space group: R3
Streak: Pale green