Parnauite

Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Basic hydrated copper arsenate sulphate
Chemical Formula: Cu9(AsO4)2(SO4)(OH)10.7H2O
Method(s) of Verification: Gwaith-yr-Afon Mine - XRD (Natural History Museum, London).

Chemical Group:

  • Arsenates

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: parnauite occurs in the oxidation zones of some copper deposits in which arsenic minerals are present in the primary assemblage. It is, however, uncommon compared to some other arsenate minerals such as olivenite. Associated minerals likely to occur with parnauite include cuprite, malachite and a variety of arsenates.
Occurrence in Wales: a rare Welsh species with only one locality, discovered in the early 1990s, in Central Wales (Rust & Mason, 1994).

Key Localities:

  • Gwaith-yr-Afon Mine, Goginan, Ceredigion: parnauite occurs rarely as pale blue-green thin drusy crusts lining small cavities in quartz and also as coatings on corroded chalcopyrite. Much more rarely, scattered lath-like crystals to 0.75 mm have been observed. Associated minerals include chrysocolla, brochantite, malachite and tyrolite (Rust & Mason, 1994).

References:

  1. Rust, S.A. & Mason, J.S., 1994. An unusual occurrence of arsenate minerals at Gwaith-yr-Afon mine, Dyfed, Wales. Journal of the Russell Society, 5(2), 109-113.