Formula: Cu3(CO3)2(OH)2
Origin of name: From Persian lazhward = blue
Crystal system: Monoclinic
Crystal class: 2/m
Twinning: Rare on {-101}, {-102} or {001}
Unit cell: a = 5.01 Å, b = 5.84 Å, c = 10.34 Å, b = 92.5°
Colour: Light blue to very dark blue, usually azure blue
Diaphaneity: Transparent to sub-translucent
Habit: Crystals varied in habit and often modified; tabular or short prismatic, equant, or rhombohedral; massive, stalactitic, earthy, nodular concretions
Hardness: 3.5 to 4
Specific gravity: 3.773
Cleavage: 3; {011} slightly imperfect, {001} fair, {110} in traces
Streak: blue, lighter than colour
Synonyms/varieties: Blue copper, chessylite
Comments: Luster of massive varieties sometimes dull. Secondary mineral in the oxidised zone of copper deposits, often together with malachite.
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