The Legnica deposit is one of the most prospective in the context of future lignite mining. Its extraction will be inseparable from the removal of the rocks of the overburden, the volume of which is very large. Due to the raw material properties, some of the rocks can be classified as accompanying minerals. The raw material identification of overburden sediments in the Legnica lignite deposit is insufficient. So far, they haven’t been the subject of detailed and comprehensive research to prove their usefulness. The article was a summary of the knowledge on this subject. The following should be included in the accompanying minerals: Quaternary sands and gravels, tertiary sands and clays (Poznan clays). They are present in two colour variants in the Legnica deposit - and fiery. The mineral composition of greenish-blue clays allows them to be included in illite-kaolinite- smectite varieties, in turn fiery clays as kaolinite-illite-smectite varieties. The tertiary clays are a very useful raw material for the production of building materials. In addition, they are potential mineral sorbents due to the nature of the association of clay minerals (occurrence of montmorillonite). They also show suitability for building waterproofing barriers. Quaternary gravels and sands, developed in the overburden Legnica deposit are differentiated raw materials. Some of them are raw materials for the construction industry. The glacial tills can be used as a component of ceramic mixtures. Tertiary sands can be used as a proppant material. The information on the raw material properties of these sediments will be one of the essential criteria for their treatment as accompanying minerals. Minerals accompanying those developed in the Legnica deposit should be exploited and deposited selectively. The creation of anthropogenic deposits accumulating these minerals will provide the possibility of their use for decades after the termination of operation.

The article characterizes geological formations occurring in the Polish lignite deposits having the characteristics of raw materials, i.e. accompanying minerals, giving their location, quality characteristics, estimated resources and potential applications. Attention has also been paid to the economic suitability, e.g. in infrastructure works and for the reclamation of many geological formations found in the overburden, classified as so-called earth or rock mass. There are also raw materials of sorption properties representing a huge potential source of minerals valuable for the economy and environmental protection. This refers to e.g.: beidellite clays from Bełchatów, Poznań clays from the region of Konin and Adamów, lacustrine chalk from Bełchatów, as well as Mesozoic limestone from the lignite bedding in Bełchatów. The reasons for the unsatisfactory use of accompanying minerals have been given. The authors described the methods used in the mining operation and processing of associated minerals, also applicable in Poland, as the legal basis for the extraction of these minerals and the economic and financial conditions. They stressed the need to protect mined not associated minerals used by the construction of anthropogenic deposits. This activity primarily requires regulating the legal status of these deposits and the development and application of an economic and financial system that stimulates the economy of these minerals. In summary, the necessary actions were taken to increase the use of the accompanying minerals and their contribution to the balance of mineral resources in the country.

The Tertiary lignite formations in the Bełchatów deposit, along with coal, are built of plastic, weakly compact and loose rocks. Their physical and mechanical parameters, don’t pose operational problems. However, varieties of a different lithological character and physical-mechanical properties rocks, causing difficulties when mining the overburden rocks, appear within them. These include: Mesozoic limestones, Tertiary sandstones and conglomerates, as well as Quaternary iron feldspar rocks. The article features a lithological characterization as well as values of basic physico-mechanical parameters. They form the basis of the geological engineering classification and decide about their difficult workability. The possibilities of their raw material utilization were also discussed.