In the district around Port Glasgow, on the south coast of the eastern peninsula, are the Boioro limestones, also of unknown age; they are lead-coloured, brecciated limestones with interbedded dolerites.
The mining product next in value to coal in 1908 was copper, taken chiefly in Carbon county in a zone of brecciated quartzite underlying schist, the original ore being chalcopyrite, with possibly some pyrite, a secondary enrichment, which has produced important bodies of chalcocite in the upper workings, but these are replaced by chalcopyrite at greater depth.