- Metamorphic: low-grade
- 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.
- 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.