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Pyrophyllite (Photo) [abbr. Prl ]

Year of discovery: 1829 (Pyshminskoe deposit, Russia), 1875 (Japan)

Locality list: 339 localities of pyrophyllite

• Al₂Si₄O₁₀(OH)₂
• [Al³⁺₂][(OH)₂|(Si₂O₅)₂]^6-

• Class: Talc-Pyrophyllite group
• Class: Phyllosilicate - Hydroxide
• Insoluble in: HCl
• Fluorescence: Long UV excitation (Yellow)
• Formed by alteration of Topaz.

• Al => Fe³⁺: Ferripyrophyllite

• Al₂ => Mg₃: Talc
• Al₂ => Fe²⁺₃: Minnesotaite
• Al₂ => Ni₃: Willemseite

• Color: White, Pale green, Pale blue
• Streak: White
• Luster: Pearly
• Diaphaneity: Translucent, Opaque

• Habit: Thin platy

• Cleavage: Perfect on {001} (1 plane)
• Hardness: 1-2
• Density: 2.8

• System: Triclinic (1A, high temperature), Monoclinic (2M, low temperature) (Layer-stacking polytype)
• Group: (-1), P(-1)
• Lattice: a=5.2, b=9.0, c=9.3, α=91.2, β=100.5, γ=89.6

Etymology: Pyr (Fire) -phyllon (leaflet) in Greek