Carrolite

Tiny crystals of Ni-rich carrollite were first observed at Tsumeb by Geier (1973-74), who noted that they are barely visible to the naked eye and associated with equally rare crystals of the cobalt sulphide linnaeite (Co₃S₄). These minerals are generally visible only by reflected light microscopy.

Pinch and Wilson (1977) described "… tiny, light steel-gray crystals [of carrollite] visible under the microscope".

Lombaard et al. (1986) considered carrollite to be extremely rare.

Hughes (1987) described Ni-rich carrollite intergrown with and replaced by galena, and as skeletal and subhedral grains in bornite. His EMPA analysis of carrollite from West 80 on 30 Level yielded the following average composition (based on four analyses): Co 26.2 wt %; Ni 12.4 wt %; Cu 21.1 wt %; Fe 0.9 wt %; S 40.2 wt % (total wt % = 100.8).

Gebhard (1999) noted the occurrence of carrollite as microscopic blebs in massive sulphide ore.