We have studied the composition and structure of the products of initial crystallization stage of melt with the following composition (in mol. %): Fe 31.90, Cu 16.03, Ni 1.70, S 50.31, and by 0.03 Ru and Rh. Directional solidification of the sample was carried out in the region of primary crystallization of pyrrhotite solid solution (Poss) in the Fe-Cu-Ni-S system. Results of optical microscopy and SEM-EDS showed that the distribution of the main components and Rh in the sample agrees with the theory of directed crystallization. Refractory ruthenium sulfide RuS2 (structure type FeS2, pyrite), formed in the sulfide melt, plays the part of mechanical dopant. On cooling of the crystallized sample, Poss partly decomposes to form nonstoichiometric isocubanite Cu1.1Fe2S3 (Icb*). On further cooling, Icb* decomposes into stoichiometric isocubanite CuFe2S3 (Icb) and Cu3Fe4S7 phase. These phase reactions do not influence the distribution of Rh and Ru in the sample volume. Crystallographic parameters, features of modulation and spatial orientation of pyrrhotite and cubanite phases of sulfide matrix were determined.