Formula: (K,Na)2(UO2)2Si5O13.4H2O
Origin of name: for Alice Mary Dowse Weeks (1909-1988), professor of mineralogy, Temple University (Philadelphia, USA), mineralogist with the U.S. Geological Survey, noted specialist in the mineralogy of uranium and vanadium
Crystal system: Orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 14.26 Å, b = 35.88 Å, c = 14.20 Å
Colour: Yellow
Diaphaneity: Transparent to translucent
Luster: Waxy to silky
Habit: crystals acicular, in small spherulites, bladed
Hardness: 1-2
Specific gravity: about 4.1
Cleavage: 2; prismatic distinct
Tenacity:
Streak: Yellow
Synonyms/varieties:
Comments: Radioactive
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