The review provides an overview and description of the results obtained from our coal studies conducted over the past two decades. It places specific emphasis on crucial parameters, including the ash content and calorific value of lignite, which is the main energy source in Mongolia. Through the research, we observed that the ash content of coal can be estimated by analyzing the concentrations of key chemical elements, including Ca, Fe, and Sr. The results of ash content obtained from the x‐ray fluorescence analysis are consistent with the outcomes of chemical analysis. Furthermore, we established an inverse linear correlation between the calorific value of coal and its ash content. Building upon this correlation, we have proposed a method that allows for the direct determination of coal calorific value without relying on calorimetric measurements.