The NG tooL is used to record naturally occurring gamma radiation. Gamma ray measurements are used for geologic correlation, depth control, and computing shale and clay volumes. Shale volume data can then be applied to correct the apparent porosities indicated by the acoustic, neutron, and density logs. When wellbore conditions are not favorable for a definitive SP response, a gamma ray curve is recorded in its place. Total count natural gamma is the most widely used downhole geophysical measurement. Applications range from basic lithology determination to advanced uranium exploration.