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Rhönite, Rhonite

Year of discovery: 1907 (Rhön, Germany), 1931 (Japan)

Locality list: A locality of rhönite

• Ca₂Mg₆Si₆O₂₀
• (Ca,Na)₂(Mg,Fe²⁺,Fe³⁺,Ti)₆(Si,Al)₆O₂₀
• [Ca²⁺₂][Mg²⁺₆][O₂|(SiO₃)₆]^16-

• Class: Rhönite (Rhonite) group < Sapphirine supergroup
• Class: Inosilicate (Single chain) - Oxide
• Radioactive: Very weak

• Mg₄Si₄ => Fe³⁺₄Al₄: Dorrite

• Color: Reddish brown, Black
• Streak: Reddish brown
• Luster: Vitreous
• Diaphaneity: Translucent-Opaque

• Cleavage: Good on {010} and {001} (2 planes)
• Hardness: 5-6
• Density: 3.6

• System: Triclinic (8Å) (Layer-stacking polytype)
• Group: (-1), P(-1)
• Lattice: a=10.5, b=10.9, c=9.2, α=101.4, β=97.0, γ=130.0