Jamesonite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead iron antimony sulphide
Chemical Formula: Pb4FeSb6S14
Method(s) of Verification: Bwlch Mine - XRD & EMPA (Bevins et al., 1988).

Chemical Group:

  • Sulphosalts

Geological Context:

  • Hydrothermal: epithermal polymetallic veins & pipes
Stibnite intergrown with other Pb-Sb minerals, including jamesonite, from Bwlch Mine. The specimen measures 11 cm x 6 cm. Specimen NMW 85.70G.M.34, ex R.W. Barstow Collection, © National Museum of Wales.
Introduction: jamesonite tends to occur in low-temperature Pb-Sb-(Au) assemblages in veins and stockworks. It is one of a number of sulphosalt minerals that are so similar in colour (metallic dark grey), habit (capillary crystals) and mineralogical association (stibnite-dominated assemblages) that confident identification in hand specimen is a risky business. Analytical confirmation (and particularly X-ray diffraction and electron microprobe analysis) is the only safe identification method with such minerals.
Occurrence in Wales: antimony-rich mineralization is uncommon in Wales, but one small mine at Bwlch, near to Conwy in North Wales worked stibnite-dominated antimony ore. Jamesonite was tentatively identified at the mine by Russell (1944) and later confirmed by Bevins et al. (1988).

Key Localities:

  • Bwlch Mine, Deganwy, Gwynedd: jamesonite occurs as small hair-like capillary crystals associated with stibnite and quartz (Russell, 1944; Bevins et al., 1988).

There are no key localities for this specimen.

References:

  1. Bevins, R.E., Alderton, D.H.M. & Horak, J.M., 1988. Lead-antimony mineralisation at Bwlch Mine, Deganwy, Wales. Mineralogical Magazine, 52, 391-394.
  2. Russell, A., 1944. Notes on some minerals either new or rare in Britain. Mineralogical Magazine, 27, 1-10.

There are no references for this specimen.