There are many works devoted to the internal structure of pyrite, relating mainly to pyrite deposits. This article is devoted to the structure of pyrite formed metasomatically in magnetite ores and skarns of the Sarbaisky contact-metasomatic iron deposit. The internal structure of pyrite was studied by means of electrolytic etching using 10‑20% NH₄OH solution as an electrolyte. This revealed the allotriomorphic and hypidiomorphic grain structure of aggregates and the shape of individual grains. Outside the ore body, the cube shape dominates, whereas within the ores pentagondodecahedrons and octahedrons are most characteristic, often in combination with the cube. Therefore, for random sections of pyrite the shape of pentagons, hexagons, various trapezoids, and less often squares is quite characteristic ...

The method of imprint has been known for a long time. For the first time it was proposed in 1906 by V. Bauman and E. Gein for the determination of iron and manganese sulfides in various grades of steel, and later – by R. O. Zhirkovsky and a number of Swiss researchers for diagnosis of opaque minerals in polished slides. In the Soviet Union, further development and improvement of the method was carried out by S. A. Yushko and I. S. Volynsky, and recently – V. I. Tikhomirov ...

The article presents new data on intrusive rocks of the Sarbaiskoye deposit, obtained as a result of the works of the geological party of the Leningrad Mining Institute. Sarbaiskoye magnetite ore deposit is one of the largest among the deposits of the Kustanay iron ore province. I. A. Kochergin and G. A. Sokolov consider this deposit to be a contact‑metasomatic deposit, confined to the contact of a multiphase intrusion of diorite‑porphyrites with volcanogenic‑sedimentary rocks of the Lower Carboniferous. Among the intrusive rocks I. A. Kochergin distinguishes: 1) pre‑ore: [a) diorite‑porphyrites of the main intrusion; b) vein diorite‑porphyrites; c) metadiorite‑porphyrites]; 2) post‑ore: [a) vein quartz diorite‑porphyrites; b) syenite‑porphyrites: [according to G. A. Sokolov, microgranite porphyries].

The Sarbaiskoye deposit of magnetite ores in the Kustanay region lies among deformed and metamorphosed Paleozoic rocks of monoclinal bedding, dipping to the west at an angle of 45-50° and overlain by horizontally bedded Meso‑Cenozoic sediments with a thickness of 70-130 m. E. A. Mazina attributes the ore‑hosting volcanogenic‑sedimentary sequence to the Lower Carboniferous (Middle‑Upper Viséan–Namurian).