Alumoklyuchevskite

Formula:  K₃Cu₃AlO₂(SO₄)₄

Origin of name:  From aluminum and klyuchevskite

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 18.432 Å, b = 5.139 Å, c = 18.69 Å, b = 101.12°

Colour:  Dark green

Diaphaneity: Transparent

Luster: Vitreous

Habit:  Aggregates of acicular crystals to 1 mm long

Hardness:  2-2.5

Specific gravity:  3.1

Cleavage:  1; along (001) perfect

Tenacity:

Streak: Light green

Synonyms/varieties:

Comments:  Aluminum analog of klyuchevskite; turns white on exposure to air. Formed under volcanic exhalation.