Radiometry methods as the Gamma-ray spectroscopy consists of mapping the occurrence of naturally occurring Potassium40 (K) concentration, the equivalent Uranium238 (U) and Thorium232 (Th) concentration. Gamma rays are faint bursts of very high frequency (highly energetic) electromagnetic waves that are spontaneously emitted by the nuclei of certain isotopes of some elements. They have much shorter wavelengths than most other electromagnetic rays, including X-rays, and therefore, are less penetrating. Only a limited number of isotopes of the natural elements emit gamma rays; and among these, the three abovementioned are common enough within earth materials to make them geologically useful.
In the radioactivity decay process of these elements gamma radiation is emitted, and this emission rate can be detected by special instruments called spectrometers. These measurements allow to estimate the concentrations of potassium, uranium and thorium in the analyzed sample which can be very useful for mineral exploration and geological mapping.