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Hydrotalcite

Year of discovery: 1842 (Dypingdal deposit, Norway), 1974 (Japan)

Locality list: 13 localities of hydrotalcite

• Mg₆Al₂CO₃(OH)₁₆,4H₂O
• [Mg²⁺₆][Al³⁺₂][(OH)₁₆|CO₃]^18-,4H₂O

• Class: Hydrotalcite group < Hydrotalcite supergroup
• Class: Carbonate - Hydroxide - Hydrate

• Mg => Ni: Takovite

• Al => Mn: Desautelsite
• Al => Fe: Pyroaurite, Sjögrenite(Sjogrenite)
• Al => Cr: Stichtite

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

• Cleavage: Perfect on {0001} (1 plane)
• Hardness: 2
• Density: 2.0

• System: Hexagonal (2H), Trigonal (3R) (Layer-stacking polytype)
• Group (2H): 6/mmm, P6₃/mmc
• Group (3R): (-3)m, R(-3)m
• Lattice (2H): a=3.1, c=15.3
• Lattice (3R): a=3.1, c=23.2