Variscite

Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Aluminium phosphate hydrate
Chemical Formula: AlPO4.2H2O
Method(s) of Verification: Pwll-du Head - XRD (National Museum of Wales, NMW X-1156 and 1236)

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Variscite from Pwlldu beach, Gower, South Wales. Field of view 4.5 mm wide. National Museum of Wales Collection (NMW 2001.52G.M.1). Photo T.F. Cotterell, © National Museum of Wales.
Introduction: variscite is typically deposited under surface conditions in cavities and breccias as a result of phosphate-bearing meteoric waters reacting with aluminous rocks.
Occurrence in Wales: variscite is a rare mineral in Wales, recorded only recently at two adjoining localities on the Gower in south Wales. It was discovered by Plant & Jones (2001) in debris derived from a small limestone quarry at Pwll-du Head, previously recorded for its occurrence of wavellite. Variscite typically forms in association with wavellite and has subsequently been identified on the nearby storm beach at Pwll-du, always as minute spherical patches in wavellite-bearing chert.

Key Localities:

  • Pwll-du Head, Bishopston, Gower, South Wales: small (<1 mm), colourless to orange-yellow rosettes of variscite associated with sea-green wavellite found in quarry debris at the foot of the bank (Plant & Jones, 2001).
  • Pwll-du storm beach, Bishopston, Gower, South Wales: similar to the occurrence at Pwll-du Head. Tiny pearly white spherical patches occur embedded within broken wavellite sprays collected from pebbles and boulders on the storm beach (T.F. Cotterell, unpublished data).

References:

  1. Plant, S.P., & Jones, I.E., 2001. Wavellite and variscite on Gower, Swansea, South Wales. Journal of the Russell Society, 7 (2), 79-81.