Crystal System: Hexagonal
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Nickel arsenide
Chemical Formula: NiAs
Method(s) of Verification: Great Orme Copper Mines - EMPA (Parnell, 1988).

Chemical Group:

  • Sulphides

Geological Context:

  • Igneous
  • Hydrothermal: Mississippi Valley Type veins
  • Hydrothermal: epithermal polymetallic veins & pipes
Introduction: nickeline (also known as niccolite) is found most commonly in massive magmatic sulphide deposits and in silver deposits where it is associated with other Ni-Co arsenides and native silver. Neither of these associations are known from Wales. It may, however, occur as a trace mineral in other types of ore deposits.
Occurrence in Wales: nickeline is only known from a single locality in Wales. However, this is perhaps unsurprising as the classic nickeline-bearing associations do not feature in the otherwise considerable diversity of Welsh mineral deposits.

Key Localities:

  • Great Orme Copper Mines, Llandudno, Gwynedd: cobaltian nickeline with the formula (Ni0.82Co0.18)0.95As has been identified as microscopic grains occurring on fractures within uraniferous hydrocarbon from the Ty Gwyn section of these mines (Parnell, 1988).


  1. Parnell, J., 1988. Mineralogy of uraniferous hydrocarbons in Carboniferous-hosted mineral deposits, Great Britain. Uranium, 4, 197-218.