Zincostaurolite

Formula: []₄Zn₄Al₁₆(Al₂[]₂)Si₈O₄₀[(OH₂)O₆]

Origin of name: The name reflects its composition, zinc dominant analogue of staurolite

Crystal system: Monoclinic

Crystal class: 2/m

Twinning: 

Unit cell: a = 7.853, b = 16.534, c = 5.639 , β = 90.00°

Colour: Colourless

Diaphaneity: Transparent

Luster: Vitreous, resinous

Habit: Prismatic

Hardness: 7-7.5?

Specific gravity: 3.78 (calculated)

Cleavage: Not observed

Tenacity: Brittle?

Streak: White

Synonyms/varieties:

Comments:  Breakdown of gahnite, pyrophyllite and diaspore, in meta-bauxite in karst-filled limestone