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Antigorite (Photo) [abbr. Atg ]

Year of discovery: 1840 (Antigorio valley, Italy, and Geisspfad area, Switzerland), 1926 (Japan)

Locality list: 191 localities of antigorite

• Mg₃Si₂O₅(OH)₄
• (Mg,Fe²⁺)₃Si₂O₅(OH)₄
• Mg²⁺₃[(OH)₄|Si₂O₅]^6-
• Platy structure with wavy superstructure

• Class: 1:1 layer, Strip-Tetrahedral < Modulated hydrous < Phyllosilicate subclass < Silicate class
• Class: Phyllosilicate - Hydroxide
• Soluble in: HCl (Gel residue)
• Formed above 75 degree, at higher temperature than Lizardite.

• Polymorph: Chrysotile (Monoclinic), Lizardite (below 75 degree, Triclinic)

• Mg => Mn: Caryopilite
• Mg => Ni: Népouite (Nepouite)
• Mg => Fe: Greenalite

• Color: Green
• Streak: Pale green
• Luster: Vitreous
• Diaphaneity: Translucent

• Habit: Platy

• Cleavage: Good on {001} (1 plane)
• Hardness: 3.5-4
• Density: 2.5

• System: Monoclinic
• Group: m, Cm
• Lattice: a=43.5, b=9.3, c=7.3, β=91.1

• Non-coexist: Quartz

Synonym: Picrolite