Stibnite

Formula: Sb₂S₃

Origin of name: from Greek stibi and Latin stibium, names for metal antimony

Crystal system: orthorhombic

Crystal class: 2/m 2/m 2/m

Twinning: rare on {130}, {120} or perhaps {310}

Unit cell: a = 11.23 Å, b = 11.31 Å, c = 3.839 Å

Colour: pale to dark lead-gray, may tarnish iridescent, bluish or blackish

Diaphaneity: 

Luster: metallic, often brilliant

Habit: crystals slender prismatic, vertically striated often bent or twisted, bladed, columnar, massive, compact

Hardness: 2

Specific gravity: 4.63 to 4.66

Cleavage: 3; {010} perfect, easy, {100} and {110} imperfect

Tenacity: subconchoidal to uneven, flexible

Streak: gray to dark gray

Synonyms/varieties: antimonite

Comments: dimorphous with metastibnite