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Nacrite

Year of discovery: 1807 (Einigkeit mine, Germany), 1949 (Japan)

Locality list: 43 localities of nacrite

• Al₂Si₂O₅(OH)₄
• [Al³⁺₂][(OH)₄|Si₂O₅]^6-

• Class: Kaolinite subgroup < Serpentine-Kaolin group
• Class: Phyllosilicate - Hydroxide
• Polytypes are not recognized as independent mineral species, but clay minerals are exceptions.
• Formed at higher temperature than Dickite.

• Polymorph: Halloysite-7Å (Monoclinic)

• Color: White, Gray, Pale brown
• Streak: White
• Luster: Pearly
• Diaphaneity: Transparent

• Cleavage: Perfect on {001} (1 plane)
• Hardness: 2-2.5
• Density: 2.6

• System: Monoclinic (1Md, 2M₁, Dickite), Monoclinic (2M₂, Nacrite), Triclinic (A, Kaolinite) (Layer-stacking polytype)
• Group: m, Cc
• Lattice: a=5.1, b=8.9, c=14.4, β=113.7