The article presents results of the detailed petromagnetic analysis of the core samples of the potassium salts of the Kungurian potassium salt complex in the Gremyachinskoe deposit (Volgograd region), which allowed for obtaining additional information on the stratigraphic rhythmicity and for substantiating the correlation levels. The connection between magnetic susceptibility variations and changes in the unsoluble residue content over sylvinite layer section has been identified and used as a basis for the development of a new express petromagnetic method of the sylvinite quality evaluation. This method involves no microscopic studies of the thin sections and eliminates the need for the prolonged unsoluble residue extraction through salt dissolving.