Rosiaite

Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Distribution: Rare
Chemical Composition: Lead antimony oxide
Chemical Formula: PbSb2O6
Method(s) of Verification: Bwlch Mine - IR & XRD (Ryback & Francis, 2001).

Chemical Group:

  • Antimonates and Antimonites

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
Introduction: rosiaite is a very rare secondary mineral named after the town where it was discovered in Italy. Rosiaite forms in association with other secondary antimony species, including bindheimite, in oxidized antimony deposits dominated by primary stibnite.
Occurrence in Wales: the mineral which, was to be later named rosiaite was discovered by G. Ryback in 1985 on a specimen collected by himself in 1955 from Bwlch Mine near Deganwy in Gwynedd. However, identification of this phase which, occurs as a very thin, light orange-brown crust coating stibnite and buff coloured cellular bindheimite, defied identification by both IR and X-ray powder analyses during the 1980’s. In 1996 when, the new mineral rosiaite was described (Basso et al., 1996) it was noted that a match was made with the Bwlch Mine material (Ryback & Francis, 2001).

Key Localities:

  • Bwlch Mine, Deganwy, Gwynedd: rosiaite occurs as a very thin light orange-brown crust composed of minute (<50 µm across) stacked rounded platelets associated with buff-coloured cellular bindheimite on stibnite in a small (several mm across) cavity in mineralized ignimbrite (Ryback & Francis, 2001).

References:

  1. Basso, R., Lucchetti, G., Zefiro, L. & Palenzona, A., 1996. Rosiaite, PbSb2O6, a new mineral from the Cetine mine, Siena, Italy. European Journal of Mineralogy, 8, 487-492.
  2. Ryback, G. & Francis, J.G., 2001. Rosiaite from Bwlch mine, Deganwy, Conwy, Wales. Journal of the Russell Society. 7(2), 88.