Evaluation of radiological hazards associated with some Egyptian marble and granite rocks

The aim of the current study is to evaluate the radioactivity estimate the radiological risk of some granites and marbles rocks and explaining the cause of increased radioactivity in some types of rocks. The radioactivity of some granites and marbles produced in Egypt were determined by using a Germanium detector. Three types of marble (Breshia, Galala, and Trista) and three types of granite (Gandola, White Halayeb, and Red Aswani) were collected. All marble samples show low radioactivity with average activity concentrations of 20 ± 2, 4.50 ± 0.5, and 6.70 ± 1.2 Bqkg^{- 1} for ²²⁶Ra, ²³²Th, and ⁴⁰K respectively. Granite samples have higher activity concentration with averages of 152 ± 7, 129 ± 8, and 1228 ± 15 Bqkg^{- 1} for ²²⁶Ra, ²³²Th, and ⁴⁰K respectively which exceed the world average values of soil (32,45,412 Bqkg^{- 1} for ²²⁶Ra, ²³²Th, and ⁴⁰K respectively) excluding Granite G.2 (white Halayeb) as it shows an insignificant level of radioactivity. The annual effective doses of marble samples Breshia, Galala, and Trista were measured to be 4.42 ± 0.4; 158 ± 14 and 153 ± 15 µSvy^{- 1}, and 1008 ± 147, 80 ± 7 and 987 ± 45.0 µSvy^{- 1} for the granite samples Gandola, White Halayeb and Red Aswani respectively. The radiation hazard parameters show a higher value for granite samples than marble samples, primarily due to the presence of potassium feldspar minerals in these types of granites. marbles were observed to be radiologically safer than granite because they possess a neglected ⁴⁰K content and a trace quantity of uranium and thorium. Moreover, the minimum potassium content is enough to make a rock radiological unsafe due to ⁴⁰K only being determined to be about 13.2%.