Formula: CaMnFe2Fe2(PO4)4(OH)2 . 8H2O
Origin of name: For R. Jahns, American geologist
Crystal system: Monoclinic
Crystal class: 2/m
Twinning:
Unit cell: a = 14.94 Ǻ, b = 7.14 Ǻ, c = 9.93 Ǻ, β = 110.1°
Colour: Nut brown, purplish brown, yellow, orange, green-yellow
Diaphaneity:
Luster: Vitreous to subadamantine
Habit: Crystals short to long prismatic, often tabular; parallel aggregates
Hardness: 4
Specific gravity: 2.71
Cleavage: 1; {001} good
Tenacity: Brittle
Streak:
Synonyms/varieties:
Comments: Three distinct species with the extensions -(CaMnFe), -(CaMnMg) and -(CaMnMn) indicating he predominent cations in the first three positions in the formula
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