Luzonite

Crystal System: Tetragonal
Status of Occurrence: Confirmed Occurrence - 2nd UK recording
Distribution: Rare
Chemical Composition: Copper arsenic sulphide
Chemical Formula: Cu3AsS4
Method(s) of Verification: Dolyhir Quarry - XRD (National Museum of Wales, NMW X-1400) & EDS (National Museum of Wales).

Chemical Group:

  • Sulphosalts

Geological Context:

  • Hydrothermal: Mississippi Valley Type veins
  • Hydrothermal: epithermal polymetallic veins & pipes
Metallic luzonite within calcite-baryte cemented muddy breccia. Dolyhir Quarry. Field of view 8 mm wide. National Museum of Wales Collection (NMW 2002.51G.M.2b). Photo T.F. Cotterell, © National Museum of Wales.
Introduction: luzonite and related minerals occur in a variety of ore deposits, but the most important association is in 'high sulphidation' gold lodes (the 'enargite-type' class of gold deposits), in which the mineralization has been precipitated from high temperature and highly acidic hydrothermal fluids, typically associated with high level intrusive and subvolcanic igneous activity. Luzonite may also occur in porphyry-type copper deposits and in a relatively rare arsenic-rich subclass of Mississippi Valley Type (lead-copper-zinc) Pb-Cu-Zn-Ba vein deposits, as at the only Welsh occurrence.
Occurrence in Wales: luzonite is a rare mineral in the UK despite its abundance in some other parts of the world. The only Welsh occurrence is a relatively recent discovery at a site remarkable for its species-rich hydrothermal mineral veins - Dolyhir Quarry in the Borderlands (Cotterell et al., 2011).

Key Localities:

  • Dolyhir Quarry, Old Radnor, Powys: luzonite typically forms nodular masses, with a characteristic pinkish metallic hue, within calcite-baryte cemented muddy breccia, derived from the north-western face of the main quarry workings in 2002. Associated metallic minerals within this sub-assemblage were covelline and chalcocite.

There are no key localities for this specimen.

References:

  1. Cotterell, T.F., Green, D.I., Hubbard, N., Mason, J.S., Starkey, R.E. and Tindle, A.G., 2011. The Mineralogy of Dolyhir Quarry, Old Radnor, Powys, Wales. UK Journal of Mines and Minerals, 32, 5-61.

There are no references for this specimen.