Optically stimulated luminescence (OSL) and infrared-radiofluorescence dating determine the time of the last exposure of mineral grains to sunlight, and hence the depositional age of a sediment layer. Thermoluminescence (TL) evaluates the time of the heating-event of burnt artefacts or heated rocks and sediments. OSL/TL and IR-RF are suitable techniques to determine the timing of human activity at archaeological sites especially if organic material is poorly preserved or beyond the datable range of radiocarbon (thus providing reliable age-estimates for sedimentary deposits or artefacts of Holocene up to Middle Pleistocene age).
The most commonly used minerals for luminescence dating are quartz and K-feldspar.
The underlying principle of luminescence and IR-RF is the storage of energy in the crystal lattice of minerals, due to the presence of natural ionizing radiation in the environment. With time, increasing energy is stored in the mineral, which is partially released as luminescence (light), when the material is exposed to sunlight or heat. Hence, the luminescence is proportional to the radiation the mineral has received.