Crystal System: Monoclinic
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Copper calcium arsenate sulphate hydroxide hydrate
Chemical Formula: Cu2+9Ca2[(As,S)O4]4(O,OH)10.10H2O
Method(s) of Verification: none.

Chemical Group:

  • Arsenates
  • Sulphates

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: clinotyrolite is a secondary mineral found typically in the oxidized zone of copper-bearing ore bodies.
Occurrence in Wales: the presence of this species is as yet unconfirmed. However, a number of tyrolite occurrences have produced XRD patterns that do not match ideal tyrolite (see for example Cotterell et al., 2011), while tyrolite from Gwaith-yr-Afon Mine was described by Rust & Mason (1994) as sulphatian. Further research is required to establish the true identity of all Welsh tyrolites.

Key Localities:

There are no key localities for this specimen.


  1. Cotterell, T.F., Green, D.I., Hubbard, N., Mason, J.S., Starkey, R.E. and Tindle, A.G., 2011. The Mineralogy of Dolyhir Quarry, Old Radnor, Powys, Wales. UK Journal of Mines and Minerals, 32, 5-61.
  2. Rust, S.A. & Mason, J.S., 1994. An unusual occurrence of arsenate minerals at Gwaith-yr-Afon mine, Dyfed, Wales. Journal of the Russell Society, 5(2), 109-113.