Mineral Database

Mineral Database
Mineralogy of Wales

Pyroxmangite

Crystal System: Triclinic
Formula: MnSiO3
Status of Occurrence: Confirmed Occurrence - 2nd UK recording
Distribution: Rare
Chemical Composition: Manganese silicate
Method(s) of Verification: Nant Mine - XRD (National Museum of Wales, NMW X-1501) & EMPA (Open University).

Pyroxmangite 30 mm across from Nant Mine, Ll?n. National Museum of Wales Collection (no. NMW 58.444.GR.5d). Photo T.F. Cotterell, © National Museum of Wales.

Chemical Group:
  • Silicates
Geological Context:
  • Metamorphic : low-grade
Introduction: a rare pyroxene group mineral typically found in regionally metamorphosed manganese ore deposits and manganiferous rocks.
Occurrence in Wales: pyroxmangite was identified recently (Cotterell, 2006) on a specimen in the National Museum of Wales Mineral Collection during detailed research into the complex mineralogy of manganese ores from the Benallt and Nant mines near Rhiw.
Key Localities:
  • Nant Mine, Nant-y-Gadwen, Rhiw, Llŷn, Gwynedd: pyroxmangite forms rare orange-brown veinlets (< 0.6 mm wide) in massive rhodochrosite-rich manganese ore in National Museum of Wales specimen NMW 58.444.GR.5 (Cotterell, 2006). This specimen, collected in 1943 from the mine dumps by W. Campbell forms part of a series of manganese ore specimens donated to the National Museum of Wales in 1958 by the Science Museum (London). Broken veinlets reveal radiating aggregates of flat prismatic crystals no more than a few millimetres in length.
References:
  • Cotterell, T.F., 2006 Caryopilite and pyroxmangite from Nant Mine, Nant-y-Gadwen, Llanfaelrhys, Pen Llyn, Gwynedd, Wales  UK Journal of Mines and Minerals, 27, 51-53.