Crystal System: Trigonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Locally Abundant
Chemical Composition: Manganese hydroxide
Chemical Formula: Mn(OH)2
Method(s) of Verification: Benallt Mine - XRD (Natural History Museum, x3404).

Chemical Group:

  • Oxides & Hydroxides

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: pyrochroite is a member of the brucite group of minerals which forms as a result of the oxidation of manganese ores.
Occurrence in Wales: the occurrence of pyrochroite at Benallt Mine, Llŷn, represents the first British recording of this mineral.

Key Localities:

  • Benallt Mine, Llŷn, Gwynedd: specimens of pyrochroite from this locality are held in the collections of the the National Museum of Wales (e.g. NMW 83.41G.M.3750, ex R.J. King Collection No. K5016) and the Natural History Museum (e.g. B.M. 1945, 133). Pyrochroite on the latter has been verified by X-ray diffraction (see verification section) and is associated with hausmannite.


There are no references for this specimen.