Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - 4th UK recording
Distribution: Rare
Chemical Composition: Hydrated sodium aluminium sulphate
Chemical Formula: NaAl(SO4)2.6H2O
Method(s) of Verification: Marloes Bay - XRD at the National Museum of Wales (XRD no. NMW X-1858); Deep Navigation Pit - tentative identification by XRD at the National Museum of Wales (XRD no. NMW X-1935).

Chemical Group:

  • Sulphates
Introduction: an uncommon secondary sulphate mineral known to form as efflorescence in active geothermal systems and in oxidized pyrite-bearing alkali-rich aluminous rocks.
Occurrence in Wales: Cotterell (2009) reported probable tamarugite mixed with epsomite based on X-ray diffraction of a yellow surface coating on pickeringite from Deep Navigation Pit in the South Wales Coalfield. Undoubted tamarugite has been identified on material collected from Marloes Bay in Pembrokeshire (T.F. Cotterell/J.S. Mason, unpublished data).

Key Localities:

  • Marloes Bay, Pembrokeshire: Pale sulphur-yellow efflorescence on pale sandstone consists of albite, tamarugite, kaolinite, muscovite and minor quartz (T.F. Cotterell/J.S. Mason, unpublished data).


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