Formula: MgFe2(PO4)2(OH)2.8 H2O
Origin of name: for S.I. Ushkov, Russian naturalist
Crystal system: Triclinic
Crystal class: 1
Twinning: on {hk0}
Unit cell: a = 5.2, b = 10.7, c = 7.14, α = 108.6°, β = 106.933°, γ = 72.717°
Colour: Yellowish to orange, brown
Diaphaneity: Transparent to translucent
Luster: Vitreous to pearly on cleavages, greasy on fractures
Habit: Crystals short prismatic, equant, to 2 mm
Hardness: 3.5
Specific gravity: 2.38
Cleavage: 1; {010} perfect
Tenacity: Very brittle
Streak: White
Synonyms/varieties:
Comments:
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