The article presents the challenges faced by the hard coal mining sector in Poland. The biggest

challenge results from a decrease in the demand for coal, which was triggered mainly by the climate

policy, including the tightening of environmental standards and an increase in the efficiency of generating

units. The fundamental model of the MRÓWKA domestic coal market has been described.

The model allows for determining the marginal price of a given fuel for a given generating unit in

the system and the optimal mix of fuels to meet the energy demand. The results of the model calculations

for the baseline and alternative scenarios were presented. It has been shown that the optimal

distribution of coal mining capacities promotes the import of the discussed fuel in the north-eastern

part of the country and that the individual customer valuation leads to a decrease in the competitiveness

of the units located in the central-western part of the country. The paper also discusses the

potential impact of the domestic oversupply on the balance sheet and the price of coal. According

to the obtained results and the basic laws of economics, an oversupply of coal leads to a decrease

in prices. For the analyzed variants, the dependence of prices was estimated at PLN 0.0308 / GJ for

every million tons of the oversupply. The fall in prices is largely due to the fuel supply to units located

close to ports or railway border crossings. Based on the presented arguments it can be concluded

that the maximization of financial result from the extraction of coal should be based on an analysis

taking incremental changes in fuel prices into account.

In the world-class Cu-Ag deposits of the Legnica-Głogów Copper District (LGCD), constant bulk density values are adopted to estimate the ore and metal resources within them based on the results of previous studies of the LGCD deposits carried out at the stage of their exploration and documentation: 2.6 Mg/m3 for the carbonate series, 2.5 Mg/m3 for the shale series, and 2.3 Mg/m3 for the sandstone series. The main purpose of research was to analyze the range of possible differences at local scale of observation between constant values of bulk densities (hereinafter referred to as reference values) assigned during deposit documentation to the main lithological units and bulk densities of these units determined based on the results of experimental sampling of individual lithological units within the exploited copper and silver deposits (Lubin, Polkowice-Sieroszowice and Rudna). In general, when it comes to Cu-Ag LGCD deposits (or their large parts), the relative diversity of estimates of average bulk densities of ores based on the results of experimental sampling (more than 1,600 samples from different individual lithological units were collected at 500 sampling points in mining excavations) and reference values is low (with a median not exceeding 3%). The results of studies indicate, however, that the application of reference bulk densities at the local observation scale may result in significant underestimation (up to nearly 20%) or overestimation (up to 11%) of real bulk densities of the main lithological units. This may have a noticeable impact on the correct estimation of ore and metal resources in small parts of deposits and, as a consequence, hinder the reconciliation of the planned and actual ore mining production.