Crystal System: Cubic
Status of Occurrence: Confirmed Occurrence - 2nd UK recording
Distribution: Rare
Chemical Composition: Hydrated ammonium-aluminium sulphate
Chemical Formula: NH4Al(SO4)2.12H2O
Method(s) of Verification: Two-Feet-Nine Seam, Deep Navigation Colliery, Treharris - identified by XRD at the National Museum of Wales (XRD no. NMW X-1944).

Chemical Group:

  • Sulphates
Introduction: an uncommon secondary sulphate mineral in some coal deposits or as efflorescence associated with fumaroles and hot springs.
Occurrence in Wales: colourless crystallized tschermigite was identified on a specimen of epsomite from Deep Navigation Colliery during a study of halotrichite group minerals from Wales (Cotterell, 2009).

Key Localities:

  • Deep Navigation Colliery, Treharris, South Wales: colourless crystallized tschermigite occurs intergrown with massive opaque white epsomite on a specimen from the Two-Feet-Nine Seam, Deep Navigation Pit donated by T. Gwilt Cotsworth to the National Museum of Wales specimen in 1927 and accessioned as NMW 27.128.GR.2 (Cotterell, 2009).

There are no key localities for this specimen.


  1. Cotterell, T.F., 2009. A review of halotrichite group minerals in Wales. UK Journal of Mines and Minerals, 30, 43-47.

There are no references for this specimen.