Hübnerite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Manganese tungstate
Chemical Formula: Mn2+WO4
Method(s) of Verification: Diphwys Mine by XRD (XRD no. NMW X-2178) and EDS at the National Museum of Wales; Hendre Mine by XRD (no. NMW X-2195) at the National Museum of Wales. The analytical data is presented in Cotterell et al. (2010).

Chemical Group:

  • Sulphites, Chromates, Molybdates & Tungstates

Geological Context:

  • Hydrothermal: alpine type veins
Hübnerite, Hendre Mine

12 mm long dark brown, bladed, hübnerite crystal from Hendre Mine, Llanaber, Merionethshire. National Museum of Wales specimen no. NMW 2008.43G.M.9

Introduction: hübnerite is the manganese-dominant member of the wolframite group. It is generally considered to be a high-temperature mineral, found in hydrothermal veins, greisens, granitic pegmatites and as a detrital mineral in some alluvial deposits.
Occurrence in Wales: there are no significant high-temperature mineral deposits in Wales. Consequently, tungsten-bearing minerals are rare. An unusual, apparently low temperature, occurrence within alpine-type fissure veins within the Cambrian manganese ore bed is described by Cotterell et al. (2010).

Key Localities:

  • Diphwys Mine, Bontddu, Dolgellau, Gwynedd: dark brown bladed hübnerite crystals were discovered in thin (less than 3 mm wide) quartz-dominated alpine-type fissure veinlets within blocks of bedded manganese ore found near to a loading bay at the base of the incline (Cotterell et al., 2010).
  • Hendre Mine, Moelfre, Llanbedr, Gwynedd: coarse (up to 12 mm in length) dark brown bladed crystals of hübnerite occur within quartz-carbonate veins cutting pale, carbonate dominated bedded manganese ore (Cotterell et al., 2010). A number of specimens are in the collections at the National Museum of Wales (see for example NMW 2008.43G.M.9).

References:

  1. Cotterell, T.F., Mason, J.S. and Dean, A.C., 2010. Hübnerite in alpine-type fissure veinlets in the Cambrian manganese ore bed, Harlech, Wales. Journal of the Russell Society, 13, 47-52.