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Low‐temperature Pt enrichment is illustrated with reference to two hypogene platiniferous minerals: (i) a Pd–Cu‐bearing ‘Pt2HgSe3’, an unnamed phase; and (ii) hongshiite, PtCu, with up to 0.7 wt% Hg. The former has patches oxidized to a Pt–O species with curvilinear microcracks originated by desiccation. The latter displays parallel sets of Cu‐depleted, Pt–Hg‐enriched patches, along which microfractures occur. Such microstructures are interpreted to arise from two processes: (i) oxidation and formation of a hydrated Pt–O compound, which tends to succumb to a Pt‐rich alloy by deoxygenation and dehydration, leaving behind curvilinear desiccation cracks; (ii) metal leaching conducive to native Pt by removal of Cu from hongshiite via micropores that coalesce along crystallographic planes to result in reticulated microcracks. Platinum enrichment either by oxidation or metal leaching ideally produces characteristic microcracks, which may be indicative of the origin, i.e. detrital vs. supergene, of alluvial and eluvial Pt‐rich alloys.

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Palladseite (palladium selenide) and palladian gold occur as euhedral inclusions in specularite and as infill of microfractures and interstices in magnetite aggregates (host rock fragments) within specularite-rich auriferous veins (jacutinga). Palladseite has minor amounts of Pt (0.6–3.5 wt.%), Cu (2.9–3.5 wt.%), Hg (0.9–1.9 wt.%), and Ag (0.3–0.5 wt.%). The palladian gold contains up to 6 wt.% Pd, and minor Cu and Ag. Isomertieite (Pd11Sb2As2) and sudovikovite (PtSe2) are also recorded. The veins cross-cut the main tectonic foliation of the wallrock (itabirite). The feature of fracture infill and the Se-Sb-As-Hg-Cu-Ag geochemical/mineralogical signature of the Au-Pd mineralization point to a post-ductile deformation and possibly low-temperature (epithermal) origin of the jacutinga mineralization style.Palladseite is replaced locally by a Pd-rich oxidation phase. Electron microprobe analysis of alteration halos around palladseite yields 76–80 wt.% Pd. Oxygen calculated by stoichiometry accords with a monoxide compound of the type PdO. However, the measured oxygen content is lower than expected for the PdO stoichiometry, suggesting loss of volatile species, and a more ‘hydrated’ compound, such as an oxyhydroxide.