Kyanite

Crystal System: Triclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Locally Abundant
Chemical Composition: Aluminium silicate
Chemical Formula: Al2SiO5
Method(s) of Verification: all occurrences identified by polarizing microscope.

Chemical Group:

  • Silicates

Geological Context:

  • Sedimentary: allogenic (detrital)
  • Metamorphic
Introduction: kyanite has two polymorphs (minerals with the same chemicial composition but a different crystal structure) sillimanite and andalusite, each forming under particular temperature and pressure conditions. Kyanite is typically an attractive blue colour and forms under the highest pressure metamorphic conditions of the three polymorphs in peletic rock.
Occurrence in Wales: no primary metamorphic occurrences of kyanite are known from Wales, although it has been recorded as a detrital mineral in glacial sands. Strahan et al. (1909) identified kyanite from glacial sands exposed south of Castell-tôch, near Pendine, Pembrokeshire, and Griffiths & Stuart (1940) reported kyanite as a component of glacial sands at Ludchurch, Pembrokeshire.

Key Localities:

There are no key localities for this specimen.

References:

  1. Griffiths, J.C. & Stuart, A., 1940. An occurrence of detrital diaspore in South Wales. Geological Magazine, 77, 74-76.
  2. Strahan, A. Cantrill, T.C., Dixon, E.E.L. & Thomas, H.H., 1909. The geology of the South Wales Coalfield. Part X. The geology around Carmarthen. Memoirs of the Geological Survey of England and Wales. Explanation of Sheet 229.

There are no references for this specimen.