The evidence for the inverse relationship between volumetric density (apparent mass) and the natural moisture of coal in the massif is given. Natural moisture is proportional to porosity, which is inversely proportional to the bulk density. This pattern must be taken into account in the calculated method of determining the volumetric density of coal in the massif. When estimating humidity from samples, which is usually less than the humidity of the corresponding seam, the determined density of coal in the massif is higher than the density of coal in the sample. In this case, the correction for moisture has a "plus" sign, which is caused by another pattern associated with incomplete filling of the pore space with moisture in the sample, compared with the full water saturation of coal under natural conditions in the array.
