Crystal System: Not known
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Lead manganese oxide hydroxide
Chemical Formula: PbMn4+3O6(OH)2
Method(s) of Verification: Eaglebrook (Nantycagl) Mine - XRD & EDS (National Museum of Wales, NMW X-1562); Frongoch Mine - XRD (National Museum of Wales, NMW X-1820).

Chemical Group:

  • Oxides & Hydroxides

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Glossy, black, botryoidal cesarolite from Eaglebrook Mine. Field of view 18 mm across. National Museum of Wales Collection (NMW 2003.1G.M.419). Photo T.F. Cotterell, © National Museum of Wales.
Introduction: a rare supergene mineral formed as a result of the near surface alteration of galena within manganese-rich environments.
Occurrence in Wales: recently identified (Cotterell, 2006) at Eaglebrook Mine in the Central Wales Orefield during investigations looking at manganese mineralization across Wales. This discovery, which, represented the first record of this species in the British Isles was quickly followed by another at the nearby Frongoch Mine (Cotterell, 2007). Given the inconspicous nature of this species it is likely to occur elsewhere in association with Pb-bearing base metal deposits.

Key Localities:

  • Eaglebrook (Nantycagl) Mine, Ceulanymaesmawr, Ceredigion: soft, black, botryoidal manganese oxide labelled as psilomelane on a National Museum of Wales specimen (NMW 2003.1G.M.419) was shown by Cotterell (2006) to be the rare mineral, cesarolite.
  • Frongoch Mine, Devil's Bridge, Ceredigion: Soft, dull black botryoidal crusts on brown pyromorphite crystals collected from the extensive tips (Cotterell, 2007).
  • Lletty Evan-Hen Mine, Bont-goch, Ceredigion: traces of cesarolite, lithiophorite and goethite occur with coronadite on the tips (Cotterell, 2009).


  1. Cotterell, T.F., 2006. The first British occurrence of cesarolite at Eaglebrook Mine, Ceulanymaesmawr, Ceredigion, Wales. UK Journal of Mines and Minerals, 27, 36-38.
  2. Cotterell, T.F., 2007. Cesàrolite from Frongoch mine, Devil's Bridge, Ceredigion, Wales. Journal of the Russell Society, 10, 55-56.
  3. Cotterell, T.F., 2009. Supergene manganese mineralization associated with the Camdwr Fault in the Central Wales Orefield. Journal of the Russell Society, 12, 15-25.