The present work investigated the radioactivity level of the rocks samples collected from different sites
in Egypt. Twenty one rocks samples were analyzed by gamma-ray spectrometry using NaI(Tl) detector
with specially designed shield. The concentration of three natural radionuclides namely 226Ra, 232Th
and 40K has been determined and compared with chemical data obtained by XRF analysis. The results
showed that these radionuclides were present in concentration ranges (3.4–99, 7.5–134 and
93–3382 Bq kg1), (54.9–211.6, 20.71–170.5 and 2068–2344 Bq kg1) and (13–106, 29.25–106.1 and
682–755 Bq kg1) for gneiss, granite and basalt rocks, respectively, while the values were (7.5, 12.5 and
263.9 Bq kg1) and (113, 148.5 and 1672 Bq kg1) for 226Ra, 232Th and 40K in sandstone and siltstone
rocks, respectively. Also radium equivalent activity, total dose rates and external hazard index of the
rocks samples under consideration were calculated. The results showed that granite rocks contain a
high proportion of natural radioactive elements, while sandstone rocks have lesser radioactivity
concentration compared with other types of rocks.