Mineral composition of the respirable dust formed in the exploitation of a coal seam with tonstein overgrowth

It has been statistically proven that tuffogenic sediments, especially tonsteins, have a negative impact on the incidence of pneumoconiosis (silicosis) among miners in French coal basin. Therefore, the rocks attract the interest of geologists not only due to their origin and possibility of use for correlation purposes, but also as a source of dust hazard in mines. The present publication presents mineralogical tests of inhalable grain size dust formed during the exploitation of a coal seam with a tonstein overgrowth in a Polish coal mine. Mineralogical tests were conducted using an electron microscope. It has been found that the inhalable grain size dust contains two groups of components: - minerals connected with the rocks co-occurring with the coal seam (tonstein), - components connected with mining activity (anthropogenic components). The first group includes: quartz, kaolinite, micas and feldspars; the second group consists of: halite, calcium oxide, iron compounds, sulphates and compounds of chrome. The origin of the antrophogenic components varies: halite crystalises from mine waters, calcium oxide was used as grit to stop coal dust explosions, compounds of iron and chrome come from the corrosion of mining equipment, calcium sulphates were used to fill crevices and behind the support. It has been determined that the concentration of quartz in the dust is several times higher than in tonstein. It has also been noted that the sericite content increases from trace amounts in the tonstein to several percent in conglomerates of dust. The concentration of feldspars also rises slightly. The percentage of kaolinite in the dust has been observed to almost decline when compared with tonstein. The research suggests that almost all the mineral components of the rocks exploitation make their way into the mine dust. At the same time, a selection of minerals occurs according to their grain size, shape, density and cleavage.