Pararealgar

Crystal System: Monoclinic
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Arsenic sulphide
Chemical Formula: AsS
Method(s) of Verification: none.

Chemical Group:

  • Sulphides

Geological Context:

  • Hydrothermal: epithermal polymetallic veins & pipes
  • Supergene: in situ natural oxidation & weathering deposits
Introduction: pararealgar forms commonly as an alteration product of the relatively unstable arsenic sulphide realgar. The alteration process is triggered by exposure to light, hence it can form on realgar specimens unless these are kept away from light sources.
Occurrence in Wales: a powdery yellow and orange alteration product of realgar, observed on specimens collected in recent years from Dolyhir Quarry, has been suggested by some collectors to be pararealgar or orpiment on the basis of visual appearance. However, analytical studies have so far only shown the presence of realgar (Cotterell et al., 2011). Therefore the status of pararealgar as a Welsh species remains to be confirmed.

Key Localities:

There are no key localities for this specimen.

References:

  1. Cotterell, T.F., Green, D.I., Hubbard, N., Mason, J.S., Starkey, R.E. and Tindle, A.G., 2011. The Mineralogy of Dolyhir Quarry, Old Radnor, Powys, Wales. UK Journal of Mines and Minerals, 32, 5-61.