Formula: Na2KBaMn8(Ti,Nb)4Si8O32(OH,F,H2O)7
Origin of name: for Guy Perrault, Canadian mineralogist
Crystal system: monoclinic
Crystal class: 2 or m or 2/m
Twinning: swallow-tail twins
Unit cell:
Colour: orange-brown
Diaphaneity: transparent to translucent
Luster: vitreous
Habit: prismatic tabular crystals to 1 mm, swallow-tail twins
Hardness: 4
Specific gravity: 3.71
Cleavage: 1; {001} perfect
Tenacity:
Streak: pale brown
Synonyms/varieties:
Comments:
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