Nacrite

Nacrite Al₂Si₂O₅(OH)₄ is a clay mineral that is polymorphous (or polytypic) with kaolinite. It crystallizes in the monoclinic system. X-ray diffraction analysis is required for positive identification.

Nacrite
Nacrite, "Frohe Hoffnung"-shaft, Wildental, Ore Mountains
General
Category	Phyllosilicates Kaolinite-serpentine group
Formula (repeating unit)	Al2Si2O5(OH)4
IMA symbol	Ncr[1]
Strunz classification	9.ED.05
Crystal system	Monoclinic
Crystal class	Domatic (m) (same H-M symbol)
Space group	Cc
Identification
References	[2][3]

Nacrite was first described in 1807 for an occurrence in Saxony, Germany. The name is from nacre in reference to the dull luster of the surface of nacrite masses scattering light with slight iridescences resembling those of the mother of pearls secreted by oysters.