Summary: X-ray rotation photographs have been used to distinguish and select for chemical analysis the various platinum- and palladium-bearing minerals present in concentrates of Bushveld platinum ore. The name cooperite is retained for PtS, tetragonal spacegroup D4h9. The face-centred unit cell with edges a = 4·91, c = 6·10 Å., contains 4PtS. The structure is a simple type of fourfold co-ordination built up from planar PtS4 groups and tetrahedral Spt4 groups, the Pt-S distance being 2·32 Å. Laurite (RuS2) occurs as small pyritohedral-cubic crystals and has the pyrite structure with unit-cell edge a = 5·59 Å, and parameter u between 0·39 and 0·395. The third mineral (Pt,Pd,Ni)S containing about 20 % Pd and 5 % Ni, is also tetragonal with unit-cell edges a = 6·37, c = 6·58 Å. The unit cell contains 8(Pt,Pd,Ni)S, and the space-group is D4h2. The name braggite is proposed for this mineral as being the first new mineral to be discovered by X-ray methods.