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Bementite

Year of discovery: 1887 (Trotter mine, Franklin mine, USA), 1953 (Japan)

Locality list: 11 localities of bementite

• Mn₅Si₄O₁₀(OH)₆, Mn₇Si₆O₁₅(OH)₈
• [Mn²⁺₅][(OH)₆|(Si₂O₅)₂]^10-

• Class: 1:1 layer, Strip-Tetrahedral < Modulated hydrous < Phyllosilicate subclass < Silicate class
• Class: Phyllosilicate - Hydroxide
• Most of Bementite reported in Japan is Caryopilite, but there are some examples of true bementite.

• Color: Brown
• Streak: White
• Luster: Vitreous
• Diaphaneity: Translucent

• Aggregate: Massive

• Cleavage: Perfect on {001} (1 plane), Good on {100} and {010} (2 planes)
• Hardness: 6
• Density: 3.0

• System: Monoclinic
• Group: 2/m, P2₁/c
• Lattice: a=7.5, b=9.8, c=5.7, β=90.0