Formula: Fe4(AsO4)3(SO4)(OH).15H2O
Origin of name: for V. Zęka (1926-), Czech geologist
Crystal system: Orthorhombic
Crystal class: Unknown
Twinning:
Unit cell: a = 20.853 Ć, b = 7.033 Ć, c = 36.991 Ć
Colour: Grayish white, greenish white
Diaphaneity: Translucent
Luster: Dull, earthy
Habit: Found as nodules, also as cavity fillings replacing leached sulfides
Hardness: < 2
Specific gravity: 2.50
Cleavage:
Tenacity: Uneven fracture
Streak: White
Synonyms/varieties:
Comments:
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