Nacrite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Uncommon
Chemical Composition: Aluminium silicate hydroxide
Chemical Formula: Al2Si2O5(OH)4
Method(s) of Verification: Aberfan Borehole - associated with dickite, XRD at the Natural History Museum (X-ray no. 1901F); Trimsaran Borehole No. 2 - XRD at the Natural History Museum (X-ray no. 1902F).

Chemical Group:

  • Silicates

Geological Context:

  • Hydrothermal
Introduction: a member of the kaolinite-serpentine group and polymorphous with dickite, halloysite and kaolinite. Typically of hydrothermal origin.
Occurrence in Wales: identified in strata of Coal Measures age from two borehole cores at the Natural History Museum, London.

Key Localities:

  • South Wales Coalfield: identified in Coal Measures age strata from Trimsaran Borehole No. 2, Kidwelly, Carmarthenshire (registered as 1985 GM MI 29620) and associated with dickite in rock core from a depth of '380 to 382' feet in the Aberfan Borehole, Mid Glamorgan (1985 GM MI 33153).

There are no key localities for this specimen.

References:

There are no references for this specimen.