Mineral Database (Saesneg yn unig)

Mineral Database (Saesneg yn unig)
Mineralogy of Wales

Saddlebackite

Crystal System: Hexagonal
Formula: Pb2Bi2Te2S3
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Lead bismuth tellurosulphide
Method(s) of Verification: Electron-probe micro-analysis (EPMA) at the Natural History Museum, London (Cook et al., 2007).
Chemical Group:
  • Sulphides
Introduction: an extremely rare member of the aleksite group of Bi-Pb tellurosulphide minerals, typically found in association with gold derived from high-temperature hydrothermal or magmatic fluids. First described by Clarke (1997) from the Boddington gold deposit, Western Australia, material matching saddlebackite had previously been recognised (Spiridonov, 1995) as a possible new mineral at Kochkar, South Urals.
Occurrence in Wales: during a study of aleksite group minerals Cook et al. (2007) identified a single grain of saddlebackite on a specimen from Clogau Mine, near Dolgellau, Gwynedd, Wales.
Key Localities:
  • Clogau Mine, Bontddu, Gwynedd: a single grain of saddlebackite was identified intergrown with aleksite on specimen E.1309 at the Natural History Museum, London (Cook et al., 2007). The specimen contains pyrrhotite, chalcopyrite and galena with a telluride assemblage consisting of tellurobismuthite, hessite, aleksite and an unnamed phase with gold in a chlorite-calcite-quartz matrix.
References:
  • Clarke, R.M., 1997 Saddlebackite, Pb2Bi2Te2S3, a new mineral species from the Boddington gold deposit, Western Australia.  Australian Journal of Mineralogy, 3, 119-124.
  • Cook, N.J., Ciobanu, C.L., Stanley, C.J., Paar, W.H. and Sundblad, K., 2007 Compositional data for Bi-Pb tellurosulfides.  Canadian Mineralogist, 45, 417-435.
  • Spiridonov, E.M., 1995 Mineralogy of the metamorphosed plutonogenic gold-quartz Kochar deposit, South Urals. 1. Gold-telluride ores.  Zap. Vses. Mineral. Obshchest, 124, 24-39 (in Russian).