Tinzenite

Formula: (Ca,Mn,Fe)₃Al₂BSi₄O₁₅(OH)

Origin of name: after locality Tinzen, Val d'Err, Grisons, Switzerland

Crystal system: Triclinic

Crystal class: 1

Twinning:

Unit cell: a = 8.988, b = 9.175, c = 7.149, α = 102.9°, β = 98.1°, γ = 88°

Colour: Yellow, brownish yellow-green

Diaphaneity: Transparent to translucent

Luster: Vitreous

Habit: Fibrous to platy, as aggregates of prismatic crystals to 5 mm, massive

Hardness: 6.5 to 7

Specific gravity: 3.35-3.43

Cleavage: 4; {100} good, {001}, (110} and {011} poor (by analogy to the axinite group)

Tenacity: Brittle, uneven to conchoidal fracture

Streak: 

Synonyms/varieties: Severginite

Comments: series with manganaxinite. Found in quartz veins in manganese deposits.