Alacranite

Formula: As₈S₉

Origin of name:  For locality, the Alacran deposit, Chile

Crystal system:  Monoclinic

Crystal class:  2/m

Twinning:

Unit cell: a = 9.89 Å, b = 9.73 Å, c = 9.13 Å, b = 101.84°

Colour:  Orange-yellow, orange

Diaphaneity: Transparent

Luster:  Adamantine, greasy

Habit:  Grains flattened and prismatic, to 0.5 mm

Hardness:  1.5

Specific gravity:  3.43

Cleavage: imperfect on {100}

Tenacity: Very brittle

Streak:  Orange-yellow

Synonyms/varieties:

Comments: In hydrothermal As-S veins, also as cement in sandy gravel