Formula: (Na,Ca)2(Mn,Fe)(Zr,Ti)Si2O7(O,OH,F)2
Origin of name: Locality; Island of Laven, Langesund fjord, Norway
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell:
Colour: Colourless, light to dark yellow, brown, brownish red to blackish brown
Diaphaneity: Translucent
Luster: Vitreous to dull and greasy
Habit: Crystals prismatic; massive; acicular radial aggregates
Hardness: 6
Specific gravity: 3.51 to 3.547
Cleavage: 1; {100} perfect
Tenacity:
Streak: Yellow
Synonyms/varieties:
Comments:
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