Olivenite
Chemical compound
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Olivenite is a copper arsenate mineral, formula Cu₂AsO₄OH. It crystallizes in the monoclinic system, and is sometimes found in small brilliant crystals of simple prismatic habit terminated by domal faces. Wikipedia
Color: Olive green to yellow or brown, gray-green, grayish white
Crystal class: Prismatic (2/m); (same H-M symbol)
Crystal habit: Fibrous, globular and reniform; granular, earthy, massive
Crystal system: Monoclinic
Formula (repeating unit): Cu2AsO4OH
Mohs scale hardness: 3
Optical properties: Biaxial (+/−)