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Epidote (Photo) [abbr. Ep ]

Year of discovery: 1801 (Bourg d'Oisans, France), 1888 (Japan)

Locality list: 1,388 localities of epidote

• Ca₂Al₂Fe(SiO₄)₃(OH)
• Ca₂Al₂(Fe,Al)(SiO₄)₃(OH)
• [Ca²⁺₂][Al³⁺₂][Fe³⁺][O|OH|SiO₄|Si₂O₇]^13-

• Class: Epidote group < Epidote supergroup
• Class: Sorosilicate - Nesosilicate - Oxide - Hydroxide
• Soluble in: HCl
• Variety: Withamite (+Mn, Red)

• Ca => Pb: Epidote-(Pb)
• Ca => Sr: Epidote-(Sr)
• Ca => Ce: Allanite-(Ce)
• Ca => Y: Allanite-(Y)
• Ca => La: Allanite-(La)
• Ca => Nd: Allanite-(Nd)

• Fe => Al: Zoisite, Clinozoisite (Series)
• Fe => Mn: Piemontite
• Fe => V: Mukhinite

• Color: Yellowish green, Green
• Streak: Colorless
• Luster: Vitreous
• Diaphaneity: Transparent-Opaque

• Habit: Prismatic

• Cleavage: Perfect on {001} (1 plane), Imperfect on {110} (1 plane)
• Hardness: 6
• Density: 3.4

• System: Monoclinic
• Group: 2/m, P2₁/m
• Lattice: a=8.9, b=5.6, c=10.2, β=115.4

Etymology: Epidoses (colorful) in Greek