Crystal System: Orthorhombic
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Lead oxide
Chemical Formula: PbO
Method(s) of Verification: Frongoch Mine - visual (Rust & Mason, 1994).

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
  • Supergene: minerals on an artificial substrate
Introduction: massicot, dimorphous with litharge, is an oxidation product of lead-bearing minerals, in particular galena, and is found as a sublimation product in fumaroles.
Occurrence in Wales: a mineral showing visual similarities with massicot has been observed associated with the polymorph litharge, at Frongoch Mine in the Central Wales Orefield (Green et al., 1996).

Key Localities:

  • Frongoch Mine, Devil's Bridge, Ceredigion: minute patches of a powdery yellow phase observed in association with litharge have been suggested as massicot (Green et al., 1996).


  1. Green, D.I., Rust, S.A. & Mason, J.S., 1996. Classic British mineral localities: Frongoch Mine, Dyfed. UK Journal of Mines & Minerals, 17, 29-38.
  2. Rust, S.A. & Mason, J.S., 1994. Minerals from the Frongoch Mine, Mid Wales. British Micromount Society Newsletter, No. 39, 18-19.