Abstract The late discovery (1966) of significant nickel sulfide deposits in the Yilgarn craton was due in part to the effects of widespread intense weathering that obscured their surface expression. Even in eroded areas where host rocks are mostly fresh or only slightly weathered, the sulfides are oxidized to considerable depth and crop out as strongly leached ferruginous gossans or silicified saprolite. Massive and matrix nickel sulfides are conductors and weather electrochemically. The upper part of the sulfide body, near the water table, acts as a cathode and deeper parts act as anodes. The process is driven by access to oxygen in the ground water and may continue to great depths. Primary pentlandite, pyrrhotite, and millerite initially oxidize to a violarite-pyrite assemblage, which in turn alters to goethite and hematite to form gossan. The reactions are pseudomorphic, so that the primary fabrics may be retained and recognized in the gossan. Disseminated sulfides are surrounded by nonconducting silicates and weather in a similar manner to the ultramafic host rock; where these are adcumulates, the saprolite is commonly strongly silicified and resistant to erosion and may form an outcropping cap rock. The regolith expression of nickel sulfide mineralization is described in terms of geochemical exploration models based on relict, erosional, and depositional landform situations, illustrated with appropriate case studies. Strong leaching during sulfide weathering, minor lateral dispersion, and lateritic enrichment of nickel even over barren ultramafic rocks, all greatly reduce geochemical contrast in surface sample media. Discrimination of mineralized systems in weathered material is particularly difficult in less eroded and depositional terrain. Pathfinder element geochemistry, principally copper and platinum group elements, is widely used but has limited success in many cases.