Formula: MnFe4(PO4)3(OH)5
Origin of name: For C. Frondel, American mineralogist
Crystal system: Orthorhombic
Crystal class: 2/m 2/m 2/m
Twinning:
Unit cell: a = 13.81 Ǻ, b = 16.97 Ǻ, c = 5.182 Ǻ
Colour: Dark olive-green to greenish black, oxidizes brownish
Diaphaneity:
Luster: Vitreous to dull
Habit: Botryoidal crusts and masses, radial fibrous or fine columnar structure
Hardness: 4.5
Specific gravity: 3.48
Cleavage: 3; {100} perfect, {010} and {001} distinct
Tenacity: Uneven; brittle
Streak:
Synonyms/varieties:
Comments: Series with rockbridgeite
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