Coronadite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead manganese oxide
Chemical Formula: Pb(Mn4+)2(Mn2+)6O16
Method(s) of Verification: Lletty Evan-hen Mine - XRD and EDS at the National Museum of Wales (XRD numbers NMW X-1726 and X-1727).

Chemical Group:

  • Oxides & Hydroxides

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Soft, black, botryoidal coronadite crust from Lletty Evan-hen Mine, Penrhyncoch, Ceredigion. Specimen 9 cm long. National Museum of Wales specimen no. NMW 2007.42G.M.4a. © National Museum of Wales.
Concentric coronadite growths from Lletty Evan-hen Mine viewed in plane-polarized light. Field of view 0.7 mm across. Amgueddfa Cymru specimen no. NMW 2007.42G.M.5b. © National Museum of Wales.
Introduction: a secondary manganese mineral found in the oxidation zone above primary manganese- and lead-bearing mineral veins.
Occurrence in Wales: coronadite is one of number of base metal-bearing manganese oxides discovered in the Central Wales Orefield (Cotterell, 2009). So far it has only been identified at Lletty Evan-hen Mine, but with more research it will probably be found to occur at many more localities, albeit in small amounts.

Key Localities:

  • Lletty Evan-Hen Mine, Bont-goch, Ceredigion: coronadite is the dominant manganese oxide present on the main tips occurring as soft, black, botryoidal crusts on reddish to pink stained siltstone (Cotterell, 2009).

References:

  1. 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.