Scanning electron microscopy – a highly selective and sensitive tool for the determination of carbonate minerals with different Mg content

In this article, using a scanning electron microscope with EDS, the results of the identification of carbonate minerals differing in magnesium content in Precambrian magnesites and Triassic limestones and dolomites are presented. This technique enables the identification of mineral phases whose chemical composition differs only slightly in the content of individual elements. This is important in the case of carbonate minerals containing magnesium, because as the amount of Mg increases, successive carbonate phases are formed, starting with low-magnesium calcite and ending with magnesite. The following carbonate phases: low-Mg calcite, high-Mg calcite, proto-dolomite, ordered dolomite, de-huntite, huntite and magnesite were identified in samples collected from the Precambrian magnesite rock of the Braszowice deposit of Lower Silesia and the Triassic, Muschelkalk limestones and dolomites of Opole Silesia and Upper Silesia in Poland. Based on the results of the study, the chemical formulas of low-magnesium calcite, high-magnesium calcite, proto-dolomite, ordered dolomite, de-huntite, huntite and magnesite were formulated. The data obtained made it possible to determine the range of magnesium content in the chemical formulas of the identified carbonate phases. In addition, schematic crystal structures of the studied carbonate phases were also developed.