Chalcoalumite

Formula:  CuAl₄(SO₄)(OH)₁₂ ^. 3H₂O

Origin of name:  From composition

Crystal system:  Monoclinic

Crystal class:  2

Twinning:  Common on {110} or {010}

Unit cell: a = 17.09 Ǻ, b = 8.92 Ǻ, c = 10.22 Ǻ, β = 95.9°

Colour:  Turquoise-green, light bluish green, pale blue, bluish gray

Diaphaneity: Transparent to translucent

Luster:  Vitreous to dull

Habit:  Crystals thin triangular plates; in spherules; microcrystalline or fibrous

Hardness:  2.5

Specific gravity:  2.29

Cleavage:  1; {100} perfect

Tenacity:  Sectile, flexible

Streak: Bluish white

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