In situ measurement of the concentration of 40K, 238U, and 232Th elements in shales, pyroclastics, limestones, and dolerites in Abakaliki–Ishiagu areas was done using the gamma-ray spectrometer. The concentrations of 40K, 238U, and 232Th in these rocks are as follows: shale (380.08 ± 194.13, 32.91 ± 8.42, 89.51 ± 17.59) (Bq/kg); pyroclastics (32.91 ± 48.64, 16.19 ± 5.43, 13.47 ± 7.29) (Bq/kg); limestone (372.17 ± 131.50, 14.10 ± 3.80, 167.03 ± 34.05) (Bq/kg); and dolerite (253.57 ± 130.26, 29.83 ± 10.46, 32.50 ± 11.07) (Bq/kg), respectively. The 40K is the major source of radiation within the study area. The radionuclide concentrations increase daily in the environment due to the quarrying of these rocks. Results of radiological hazard indices for the shale, pyroclastics, limestone, and dolerite indicate that the radium equivalent dose (150.32 ± 28.84, 38.04 ± 15.48, 293.08 ± 45.61, 102.50 ± 42.92) (Bq/kg), external hazard indices (0.42 ± 0.08, 0.11 ± 0.04, 0.80 ± 0.12, 0.29 ± 0.12) (Bq/kg), internal hazard indices (0.38 ± 0.08, 0.15 ± 0.06, 0.83 ± 0.12, 0.36 ± 0.13) (Bq/kg), and annual effective dose equivalent outdoor (0.08 ± 0.02, 0.02 ± 0.01, 0.16 ± 0.03, 0.06 ± 0.03) (msvy−1) are below the world average for all the rock types. Representative gamma indices (1.09 ± 0.22, 0.26 ± 0.11, 2.10 ± 0.33, 0.75 ± 0.36) are above the world average in sedimentary rocks only. Annual gonadal equivalent dose (481.09 ± 97.22, 116.62 ± 48.51, 893.61 ± 138.55, 333.50 ± 165.77) (μsvy−1) is below the world average for the pyroclastics only, while absorbed dose rate in the air (68.97 ± 13.88, 17.01 ± 7.00, 128.21 ± 19.82, 47.70 ± 22.66) (ɲGyh−1) is above the world average for the limestone only. Excess lifetime cancer risk (0.29 ± 0.21, 0.07 ± 0.03, 0.55 ± 0.09, 0.21 ± 0.01) is above the world average. The highest radionuclide concentration occurred in sedimentary rocks.