Formula: (K,Na)3(Fe,Mn)6(Nb,Ti)2Si8(O,OH,F)31
Origin of name: from niobium and Greek for leaf for its foliated character
Crystal system: triclinic
Crystal class: 1 or 1
Twinning: Common by reflection on (001)
Unit cell: a = 5.391, b = 11.88, c = 11.66, α = 113.1°, β = 94.5°, γ = 103.1°
Colour: Brown
Diaphaneity: Translucent to opaque
Luster: Vitreous-adamtine
Habit: Polycrystalline aggregates of small flakes
Hardness: 3-4
Specific gravity: 3.42
Cleavage: 1; {001} perfect, poor on {0kl}
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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