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Cymraeg

Rammelsbergite

Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence
Distribution: Rare
Chemical Composition: Nickel arsenide
Chemical Formula: NiAs2
Method(s) of Verification: Dolyhir Quarry - optical properties in polished section (R.A. Ixer, unpublished data).

Geological Context:

Introduction: rammelsbergite belongs to the lollingite group of diarsenide minerals - lollingite being the iron-bearing member. Rammelsbergite is sometimes present as a minor phase in hydrothermal base-metal sulphide bearing mineral veins. It tends to occur more abundantly in the nickel-cobalt-silver-arsenic-bismuth (Ni-Co-Ag-As-Bi) 'five-metals' association, when it is usually intergrown with other Co-Ni arsenides and sulpharsenides. Rammelsbergite is, unusually for Fe-Co-Ni arsenides, straightforward to identify in polished section, exhibiting distinctive interference colours (brown/purple) when viewed under partly crossed polars.
Occurrence in Wales: although the \"five-metals\" association is absent from Wales, rammelsbergite has been found during recent reflected light petrological studies of base-metal sulphide bearing vein mineralization which formerly outcropped at Dolyhir Quarry in the Welsh Borders.

Key Localities:

There are no key localities for this specimen.

References:

There are no references for this specimen.