Nacrite
Al2 Si2 O5(
OH)
4 is a
clay mineral that is
polymorphous
Polymorphism, polymorphic, polymorph, polymorphous, or polymorphy may refer to:
Computing
* Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms
* Ad hoc polymorphis ...
(or
polytypic) with
kaolinite. It crystallizes in the
monoclinic
In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...
system.
X-ray diffraction analysis is required for positive identification.
Nacrite was first described in 1807 for an occurrence in
Saxony
Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...
,
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
. 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
oyster
Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not ...
s.
References
Clay minerals group
Polymorphism (materials science)
Monoclinic minerals
Minerals in space group 9
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