Chenite

Crystal System: Triclinic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Lead copper sulphate hydroxide
Chemical Formula: Pb4Cu(SO4)2(OH)6
Method(s) of Verification: Llechweddhelyg Mine and Esgair Hir Mine: both confirmed by XRD at the Natural History Museum, London.

Chemical Group:

  • Sulphates

Geological Context:

  • Supergene: post-mining oxidation & weathering deposits
Pale blue chenite microcrystal from Esgair Hir Mine in the Central Wales Orefield. Specimen and photo S.A. Rust. © S.A. Rust.
Introduction: a secondary mineral typically formed in oxidized lead and copper-bearing ore bodies and within weathered slag derived from lead and copper smelting.
Occurrence in Wales: chenite is one of a number of rare lead-copper supergene species discovered in recent years within old mine dumps in Central Wales. Formed within the post-mining environment, it is to date only known from two localities and few specimens are known to exist.

Key Localities:

  • Esgairhir Mine, Tal-y-bont, Ceredigion: an extremely limited occurrence of chenite. It has been observed as equant sky blue crystals, up to 0.4 mm in size, occurring in association with susannite (Rust, 1997).
  • Llechweddhelyg Mine, Penrhyncoch, Ceredigion: this is the first Welsh occurrence of chenite. It was found within two small cavities in altered veinstone, containing groups of translucent sky blue sub-parallel slightly rounded platy crystals (up to 1.5 mm) (Rust, 1994).

There are no key localities for this specimen.

References:

  1. Rust, S., 1997. Chenite from Esgair Hir Mine, Talybont, Dyfed. UK Journal of Mines and Minerals, 18, 16.
  2. Rust, S.A., 1994. Chenite from Llechwedd Helyg Mine, Tir-y-Mynach, Dyfed, Wales. UK Journal of Mines and Minerals, 14, 9.

There are no references for this specimen.