The major ore minerals are pyrrhotite, pentlandite and pyrite with local chalcopyrite. Supergene alteration has resulted in the formation of violarite zones near the tops of many ore shoots as well as a variety of hydrated nickel oxides. Most geologists feel Kambalda ores were emplaced at elevated temperatures as an ultramafic crystal mush consisting largely of olivine and minor chromite, and an immiscible sulfide-oxide liquid. Gravity separation produced the ore zone. The pyrite is mentioned because many Canadian deposits lack appreciable pyrite and the feeling in North America is that the pyrite is a product of sulfidization reactions during metamorphism.
Ores occur in the lower ultramafic to mafic portion of greenstone belts.
The ores appear to be layered within the greenstone sequence and are hence, cogenetic with the greenstone belts. Minor oxide phases are present in some deposits. Ores thought to form as immiscible liquid segregations within the extrusive volcanic komatiite flows.