Abswurmbachite

Formula:  (Cu, Mn²⁺)Mn³⁺₆SiO₁₂

Origin of name:  for Irmgard Abs-Wurmbach (1938- ), German mineralogist

Crystal system:  Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 9.406 Å, c = 18.546 Å

Colour:  Black

Diaphaneity: Opaque

Luster:  Metallic

Habit:  Fibrous to elongate prismatic grains 1-5 x 6-50 mm, subhedral grains 5-30 mm

Hardness:  6

Specific gravity:  4.96

Cleavage:  none

Tenacity:

Streak:  Brownish black

Synonyms/varieties:

Comments: Forms a series with braunite. Found in very low-grade, high-pressure metamorphic Mn, Al-rich quartzites