Scheelite

Crystal System: Tetragonal
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Calcium tungstate
Chemical Formula: CaWO4
Method(s) of Verification: Shadow Gully - reflected light microscopy

Chemical Group:

  • Sulphites, Chromates, Molybdates & Tungstates

Geological Context:

  • Hydrothermal
  • Metamorphic
Introduction: scheelite occurs in high temperature tungsten-bearing mineral veins, and also in contact metamorphic mineral deposits.
Occurrence in Wales: scheelite is an extremely rare mineral in Wales, typically occurring as microscopic grains and inclusions only detectable by microprobe analysis.

Key Localities:

  • Harlech Dome area, Gwynedd: rare scheelite is present with pyritic mudstones of the Haffoty Formation of Cambrian age, exposed in the Harlech Dome area (Bennett, 1987).
  • Shadow Gully, Snowdon, Gwynedd: scheelite is developed between magnetite grains within a magnetite dominated breccia-vein complex trending NW, exposed within the gully (Bevins & Mason, 1998).

References:

  1. Bennett, M.A., 1987a. The Cambrian manganese deposits of North Wales. Unpublished Ph.D. thesis, University of Leeds.
  2. Bevins, R.E. & Mason, J.S., 1998. Welsh Metallophyte and metallogenic evaluation project: Results of a Minesite Survey of Gwynedd. National Museums of Wales, Cardiff.