There are many works devoted to the internal structure of pyrite, mainly related to the deposits. This article is devoted to the structure of pyrite, formed by metasomatic way in magnetite ores and skarns of Sarbaisky contact-metasomatic iron deposit. The internal structure of pyrite was studied by means of electrolytic etching using 10-20% NH40H solution as an electrolyte. The allotriomorphic and hypidiomorphic grain structure of aggregates and the shape of individual grains were revealed. Outside the ore deposit, the cube shape dominates, whereas the ores are most characterized by pentagondodecahedrons and octahedrons often in combination with the cube. Therefore, the shape of pentagonal and hexagonal, various trapezoids, less often squares, is quite characteristic for random slices of pyrite ...