Formula: (Ca,Na)4(Ti,Nb)2Si2O11(F,OH)2
Origin of name: For A. Fersman, Russian mineralogist
Crystal system: Triclinic
Crystal class:
Twinning:
Unit cell:
Colour: Light brown to dark brown
Diaphaneity: Translucent
Luster: Vitreous
Habit: Crystals pseudotetragonal, generally distorted
Hardness: 5 to 5.5
Specific gravity: 3.44 to 3.46
Cleavage: None
Tenacity:
Streak: White with pale brownish
Synonyms/varieties:
Comments:
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