Formula: Ca(UO2)3(SeO3)2(OH)4.4H2O
Origin of name: For Dr. Paul Piret (1932- ), Professor of Crystallography, University of Louvain-la-Neuve, Belgium.
Crystal system: orthorhombic
Crystal class: mm2 or 2/m 2/m 2/m
Twinning:
Unit cell: a = 7.01, b = 17.135, c = 17.606
Colour: Lemon-yellow
Diaphaneity: Transparent to translucent
Luster: Pearly
Habit: Elongated tablets, irregular outline, up to 1 by 3 mm, acicular prisms to 5 mm
Hardness: 2.5
Specific gravity: 4.0
Cleavage: 1; {001} good
Tenacity: Fragile
Streak: Pale yellow
Synonyms/varieties:
Comments:
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