Thermoluminescence (TL) is a method applied to certain minerals, including calcite and previously heated rocks. It is based on measuring the light that they emit while being heated in a laboratory to high temperatures (approx. 500°C). The study of this light emission enables an estimation of their age, i.e. the time having elapsed since they were heated in a prehistoric hearth. This previous heating will have removed the thermoluminescence having accumulated in the mineral since it was formed, thereby resetting the chronometer to zero. Thermoluminescence originates in the exposure of minerals to radiation (alpha, beta and gamma) emitted by the natural radionuclides (families of uranium, thorium and potassium 40) contained in trace form in almost all rocks. This radiation excites the minerals, which as a result accumulate energy over time; this energy is yielded in the form of a thermoluminescent emission. The study of the thermoluminescent properties of a mineral sample and the analysis of the levels of radionuclides that it contains and which are present in its immediate environment enable an estimation of its age to be made.