Formula: (Ca,Na)(Mg,Fe)3Al5Mg(BO3)Si6O18(OH,F)4
Origin of name: after locality province of Uva, Sri Lanka
Crystal system: Hexagonal
Crystal class: 3m
Twinning:
Unit cell: a = 15.97 Å, c = 7.20 Å
Colour: brownish black, bluish black, brown, yellowish brown, may be zoned parallel to prism faces
Diaphaneity: Translucent to opaque
Luster: Vitreous to resinous
Habit: crystals short to long prismatic or equant, striated, cross sections are typically triangular with curved, convex sides
Hardness: about 7.5
Specific gravity: 3.0-3.14
Cleavage: none
Tenacity: brittle, uneven to conchoidal fracture
Streak: White, light green, light brown
Synonyms/varieties:
Comments: Piezoelectric and pyroelectric, may fluoresce weak mustard yellow under SW-UV
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