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Hydrobiotite

Year of discovery: 1882 (World), 1950 (Japan)

Locality list: 32 localities of hydrobiotite

• K(Mg,Fe)₆AlSi₇O₂₀(OH)₄,nH₂O
• K(Mg,Fe)₆(Si,Al)₈O₂₀(OH)₄,nH₂O
• [K⁺][(Mg,Fe)²⁺₆][(OH)₄|AlSi₇O₂₀]^13-,nH₂O
• 1:1 regular interstratified mineral of trioctahedral Biotite (Annite or Phlogopite) with trioctahedral Vermiculite

• Class: Trioctahedral 1:1 regular interstratified mineral < Planar hydrous < Phyllosilicate subclass < Silicate class
• Class: Phyllosilicate - Hydroxide - Hydrate
• Radioactive: Very weak

• Color: Gold, Black
• Streak: White
• Luster: Sub-Metallic
• Diaphaneity: Translucent

• Cleavage: Perfect on {001} (1 plane)
• Hardness: 2.5-3
• Density: 2.7

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=5.2, b=9.0, c=24.5, β=90.0