Mineral Database

Mineral Database
Mineralogy of Wales

Roxbyite

Crystal System: Monoclinic
Formula: Cu9S5
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Locally Abundant
Chemical Composition: Copper sulphide
Method(s) of Verification: XRD, EDS and reflected light microscopy were all used in the identification of this rare species.

Reflected light image showing roxbyite lamellae (grey) in chalcopyrite (yellow) from Dolyhir Quarry. Specimen no. NMW 2011.8G.M.34. Field of view 270 µm. Photo T.F. Cotterell, © National Museum of Wales.

Chemical Group:
  • Sulphides
Geological Context:
  • Supergene : in situ natural oxidation & weathering deposits
Introduction: a low-temperature alteration product of djurleite and other copper sulphides.
Occurrence in Wales: roxbyite is one of a number of unusual copper sulphides developed through the supergene oxidation of primary copper sulphides (namely chalcopyrite) within limestone at Dolyhir Quarry, Old Radnor. Considering its rarity worldwide, the relative abundance of roxbyite in some specimens from Dolyhir is made all the more exceptional.
Key Localities:
  • Dolyhir Quarry, Old Radnor, Powys: roxbyite is recorded in a number of parageneses at Dolyhir Quarry (Cotterell et al., 2011), but always as extremely fine-grained lamellae intergrown with chalcopyrite, djurleite or covelline within limestone.
References:
  • 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.