In context of my master's thesis I named 69 specimens of natural stone, according to valid geological classifications. Natural stone is sold under inappropriate market names with incorrect stonemasonry classification. Most common names for natural stone in the market are granite and marble, I classified the specimens at hand with 22 different names.
Samples were divided into three main groups – magmatic, sedimentary and metamorphic. The largest portion of samples are magmatic rocks, which I named as quartz granitoide, alkali-feldspar granite, alkali-feldspar syenite, syenite-granite, monzogranite, pegmatite, granodiorite, quartz diorite, monzogabbro, gabbro, anorthosite and rhyolite. I identified limestone, travertine and sandstone in the group of sedimentary rocks. I classified the metamorphic rock samples as quartzite, granulite, serpentinite, brecciated serpentinite, migmatite, mica-schist and gneiss.
I determined the mineral composition of the samples with microscopic research in transmitted polarized light. The chemical composition of the samples was determined with X-ray Fluorescence Spectrometry. Osojnik (2016) determined the specific activity of natural radionuclides - 40K, 232Th and 238U with high resolution gamma spectrometry.
The most radioactive were granitoide rocks and metamorphic rocks (migmatites, granulites) of magmatic origin. These rocks have higher share of potassium feldspar and/or mica. In some specimens accessory minerals (e.g. zircon) were confirmed in microscopic research.
The same result was obtained from comparing results of X-ray Fluorescence Spectrometry and the mineral composition of the specimens. The relation between the type of the rock and amount of potassium, thorium and uranium in it, does exist. The highest values of the elements in question are in felsic magmatic rocks of granite group and metamorphic rocks (migmatites and granulites) of magmatic origin.
The lowest values of potassium, thorium and uranium are in the sedimentary rocks, and the lowest specific activities of natural radionuclides have been measured for these. Sampled sedimentary rocks do not contain potassium feldspar, mica and accessory minerals.