Radioactivity of some Rock Types of Andhra State, India

Beta-activity has been determined for 37 rocks (12 gneisses, 7 granites, 7 charnockites. 5 calc-granulites and 6 schists) drawn from various parts of Andhra Pradesh. For 15 samples selected from the above groups, alpha-activity was also determined, for effecting a comparative study of the two sets of measurements. The present work confirms the results of previous studies which showed that the beta-activity of a rock is conditioned by the following mutually-related factors: chemical composition (Fe₂O₃: FeO ratio, silica, potash, alumina, and calcium oxide concentrations), mineralogical composition (quartz, feldspar and heavy mineral contents), and petrogenetic history. The discrepancies in the equivalent uranium content of rocks as deduced from their beta- and alpha-activities, are traced to the variations in the concentration of beta-emitting K⁴⁰ and U : Th ratios.