Formula: Al7(BO3)(SiO4)3O3
Origin of name: For E. Dumortier, French paleontologist
Crystal system: Orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell:
Colour: Blue, violet, pinkish, brown
Diaphaneity: Transparent to translucent
Luster: Vitreous to dull
Habit: Crystals prismatic, rare; massive, columnar, fibrous or granular
Hardness: 8.5
Specific gravity: 3.71 to 3.41
Cleavage: 2; {100} good, {110} imperfect
Tenacity:
Streak: White
Synonyms/varieties:
Comments:
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