Elyite

Crystal System: Monoclinic
Status of Occurrence: Confirmed Occurrence - 3rd UK recording
Distribution: Rare
Chemical Composition: Lead copper sulphate hydroxide
Chemical Formula: Pb4Cu(SO4)(OH)8
Method(s) of Verification: all elyite occurrences in Wales are based on its distinctive purple colour and association.

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
  • Supergene: in situ natural oxidation & weathering deposits
Thin blades of elyite (purple), up to 0.75 mm long, from Llechweddhelyg Mine, in the Central Wales Orefield. S.A. Rust Collection (no. 1244). Photo M.P. Cooper, © National Museum of Wales.
Violet coloured acicular elyite, from Dolyhir Quarry, Old Radnor, Powys. © D.I. Green.
Introduction: elyite is occasionally found in the oxidized zones of lead- and copper-bearing ore bodies and, more frequently, in post mining associations within mine tips or in weathered smelter slags. Its stabilization requires relatively alkaline conditions, a property it shares with its most frequent associates such as hydrocerussite, lanarkite and leadhillite group minerals. Elyite is difficult to confuse with other minerals occurring in the post-mining supergene environment due to its striking violet colour.
Occurrence in Wales: elyite was first reported from Wales by Rust & Mason (1988) from Esgairhir Mine in the Central Wales Orefield, where it occurred along with a wide range of other post-mining minerals in old mine-tips. This represented only the third UK occurrence. Three out of the four elyite occurrences in Wales are associated with mine-tip environments in which local highly alkaline conditions occur, for example due to juxtaposition of weathering sulphidic veinstone with lime-mortar debris from collapsed buildings.

Key Localities:

  • Dolyhir Quarry, Old Radnor, Powys: found on a single specimen as minute purple lath-like crystals with lanarkite in a cavity in the oxidation crust of a fragment of massive galena found in fault gouge at the top of the main sulphide vein. Unlike most elyite, this occurrence can definitely be attributed to natural in-situ oxidation of the vein material (N. Hubbard Collection).
  • Esgairhir Mine, Tal-y-bont, Ceredigion: elyite has been found on a small number of micro-specimens as violet, fan-like sprays of crystals up to 0.4 mm in length in association with covelline, anglesite, caledonite, hydrocerussite and an uncharacterized fibrous blue copper mineral (Rust & Mason, 1988).
  • Frongoch Mine, Devil's Bridge, Ceredigion: three specimens were found in the early 1990s in an area of the dumps containing much lime-mortar rubble. The elyite formed minute purple crystals and associated minerals were hydrocerussite and cerussite (Green et al., 1996).
  • Llechweddhelyg Mine, Penrhyncoch, Ceredigion: elyite occurs very rarely at this site in cavities in part-oxidized galena, where it forms small (<1 mm) purple blades associated with an uncharacterized pale green copper mineral (S.A. Rust Collection, specimen no. 1244).

References:

  1. 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.
  2. Rust, S.A. & Mason, J.S., 1988. The minerals of Esgair-Hir mine, Dyfed, Wales. UK Journal of Mines & Minerals, 5, 35-43.