Apuanite

Formula:  Fe²⁺Fe³⁺₄Sb₄O₁₂S

Origin of name:  Localite; Apuan Alps in Italy

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 8.372 Å, c = 17.974 Å

Colour:  Black

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Crystals platy or tabular; commonly massive aggregates

Hardness:  4

Specific gravity:  5.12 to 5.33

Cleavage:  1; {110} perfect

Tenacity:

Streak: Black

Synonyms/varieties:

Comments: Found in an iron deposit in barite formed by low-grade metasomatic processes at the contact between phyllites and dolostones.