Formula: Ca(Mn,Zn)2Fe3(PO4)4(OH)3 . 2H2O
Origin of name: For Erich Keck, German mineral collector
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell: a = 15.02 Ǻ, b = 7.19 Ǻ, c = 19.74 Ǻ, β = 110.5°
Colour: Brown, yellow-brown, dirty grayish brown
Diaphaneity:
Luster: Dull
Habit: Crystals to 2 mm, aggregates
Hardness: 4.5
Specific gravity: 2.6
Cleavage: 2; {001} and {100}
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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