Tenorite

Crystal System: Monoclinic
Status of Occurrence: Unconfirmed Occurrence
Distribution: Rare
Chemical Composition: Copper oxide
Chemical Formula: CuO
Method(s) of Verification: few details available on methods of identification used; Esgair Hir Mine - visual (Rust & Mason, 1988)

Geological Context:

  • Supergene: in situ natural oxidation & weathering deposits
Introduction: tenorite is a common secondary mineral in the oxidized zone of hydrothermal copper deposits and occurs as crystallized precipitate around volcanic vents.
Occurrence in Wales: tenorite has been reported from Wales on many occasions, typically associated with large copper deposits. Unfortunately, none of the discoveries have been fully verified, and being a dull, black mineral, visual identification is considered unreliable. Greenly (1919) referred to ‘melaconite’ (a synonym of tenorite, particularly the black powdery variety) in gossan, associated with the Great Lode at Parys Mountain, Anglesey. However, Greenly based his description on an earlier account by Lentin (1800), as gossan was no longer present. The massive, powdery variety 'melaconite' is also recorded by Greg & Lettson (1858), in limestone at the Great Ormes Head. Further south, ‘melaconite’ is reported by Jones & Moreton (1977) from three mines in the Central Wales Orefield while, Rust & Mason (1988) and Bevins (1994) provide additional details.

Key Localities:

  • Darren Mine, Pen-bont Rhydybeddau, Ceredigion: dull black earthy coatings associated with chalcopyrite (Jones & Moreton, 1977).
  • Esgair Fraith Mine, Tal-y-bont, Ceredigion: dull black earthy coatings associated with chalcopyrite (Jones & Moreton, 1977) and masses to 10 cm associated with chrysocolla (Bevins, 1994).
  • Esgairhir Mine, Tal-y-bont, Ceredigion: black bituminous masses to 5 mm coat chalcopyrite and chalcocite (Rust & Mason, 1988).
  • Great Orme Copper Mines, Llandudno, Gwynedd: reported in limestone by Greg & Lettsom (1858).
  • Parys Mountain, Anglesey: ‘melaconite’ is reported in gossan associated with the Great Lode (Lentin, 1800; Greenly, 1919).
  • Snowbrook Mine, Llanidloes, Powys: lustrous pitch-like masses resembling hydrocarbon and with conchoidal fracture occur as an alteration product of cuprite (Jones & Moreton, 1977).

There are no key localities for this specimen.

References:

  1. Bevins, R.E., 1994. A Mineralogy of Wales National Museum of Wales, Geological Series No. 16, Cardiff, 146pp.
  2. Greenly, E., 1919. The Geology of Anglesey. Memoirs of the Geological Survey of Great Britain, 980pp (2 volumes).
  3. Greg, R.P. & Lettsom, W.G., 1858. Manual of the Mineralogy of Great Britain and Ireland. John van Voorst, London, 483pp.
  4. Jones, J.A. & Moreton, N.J.M., 1977. The Mines and Minerals of Mid-Wales 40pp.
  5. Lentin, A.G.L., 1800. Briefe über die Insel Anglesea, vorzuglich über die dasigen Kupferbergwerke und die dazu gehorigen Schmelzwerke und Fabriken. Leipzig.
  6. Rust, S.A. & Mason, J.S., 1988. The minerals of Esgair-Hir mine, Dyfed, Wales. UK Journal of Mines & Minerals, 5, 35-43.

There are no references for this specimen.