Titantaramellite

Formula: Ba₄(Ti,Fe,Fe,Mg)₄(B₂Si₈O₂₇)O₂Cl₈

Origin of name: from titanium and taramellite

Crystal system: Orthorhombic

Crystal class: 2/m 2/m 2/m (by analogy to taramellite)

Twinning:

Unit cell: a = 12.137, b = 13.955, c = 7.134

Colour: Dark brown to black, bronze brown, purple red

Diaphaneity: Transparent to translucent or opaque

Luster: 

Habit: crystals tabular to equant, massive, granular, in anhedral grains

Hardness: 6

Specific gravity: 4.05

Cleavage: 1; {100} perfect

Tenacity: 

Streak: 

Synonyms/varieties:

Comments: series with taramellite. Found in Ba silicates near the contact with large granitic bodies. Changes to fresnoite at 960°C.