 This may be useful for interpreting the environment of deposition as kaolinite can form from feldspars in tropical soils by leaching of potassium; and low potassium readings may thus indicate the presence of one or more paleosols.The identification of specific clay minerals is also useful for calculating the effective porosity of reservoir rock.Gamma ray logs are also used in mineral exploration, especially exploration for phosphates, uranium, and potassium salts.