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Astrophyllite

• K₂NaFe₇Ti₂Si₈O₂₆(OH)₄F
• K₂Na(Fe²⁺,Mn²⁺,Mg)₇Ti₂Si₈O₂₆(OH,F)₅
• [K⁺₂][Na⁺][Fe²⁺₇][Ti⁴⁺₂][F|(OH)₄|O₂|(SiO₃)₈]^25-

• Class: Astrophyllite group
• Class: Inosilicate (Single chain) - Oxide - Hydroxide - Fluoride
• Soluble in: HCl (Decompose)
• Radioactive: Very weak

• Fe => Mn: Kupletskite (Series)

• Color: Golden, Brown
• Streak: Yellow
• Luster: Metallic
• Diaphaneity: Translucent-Opaque

• Habit: Platy
• Aggregate: Radial

• Cleavage: Perfect on {001} (1 plane), Indistinct on {100} (1 plane)
• Hardness: 3
• Density: 3.3

• System: Triclinic
• Group: (-1), P(-1)
• Lattice: a=11.8, b=5.4, c=21.1, α=90.0, β=94.0, γ=90.0

Etymology: Astro (star) - phyllon (leaf) in Greek