Insoluble remains of Lower Permian sylvinite rocks in the western and north-western framing of the Caspian depression

The paper presents the results of a study of the insoluble residue of sylvinites and sylvin-halite rocks of the Lower Permian halogen formation, common within the Perelyubsky areas (Western and Eastern), promising for industrial development (Saratov Region) and the Gremyachinsky potash deposit (Volgograd Region). A technique for studying the insoluble residue of sylvinites is presented. The types of insoluble residue are distinguished according to the form of occurrence in sylvinites and its mineral composition is characterized. The conditions for the formation of sylvine-bearing rocks are refined, taking into account the data obtained on the composition of the insoluble residue.