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Redgillite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - 2nd UK recording
Distribution: Rare
Chemical Composition: Basic hydrated copper sulphate
Chemical Formula: Cu12(SO4)2(OH)20ยท2H2O
Method(s) of Verification: XRD.

Geological Context:

Introduction: redgillite has only recently been described as a mineral (Pluth et al., 2004), although to collectors of microminerals the distinctive, pale-green lathlike crystals have become a familiar site from a number of localities since its first discovery in the 1980s. It is one of a number of rare supergene sulphates that apparently exist only within the post-mining environment - where the chemistry is dictated by rapid superficial chemical weathering of broken mixed sulphide intergrowths. Associated minerals typically include covellite and sulphate minerals such as langite, wroewolfeite, brochantite and substances which, despite having a discrete chemical composition, are as yet uncharacterised as minerals.
Occurrence in Wales: first noted by S.A. Rust on specimens collected in the late 1980's at Esgairhir Mine, a number of other sites have since been discovered in Central Wales: indeed, the majority of UK sites for redgillite are within this area. Some fine, if small, specimens have been collected from a number of sites, although, given that the mineral has only just (2004) been accepted as a new species (with the type locality being Silver Gill in the Caldbeck Fells, Cumbria), there is currently little published information available.

Key Localities:

There are no key localities for this specimen.

References:

  1. Cooper, M.P. & Stanley, C.J., 1990. Minerals of the English Lake District - Caldbeck Fells. Natural History Museum Publications, 160p.
  2. 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.
  3. Pluth, J.J., Steele, I.M. & Kampf, A.R., 2005. Redgillite, a new mineral from Caldbeck Fells, Cumbria, England. European Journal of Mineralogy (submitted MS).

There are no references for this specimen.