Thermoluminescence (or TL) is the light emitted by certain minerals when they are heated. Because the amount of light emitted increases as the sample ages, it forms the basis of the dating technique known as thermoluminescence (or TL) dating. This technique is possibly best known for its use in distinguishing modern fakes from ancient ceramics in the art world, but it has also been used to date pottery and other heated materials including burnt flint and the remains of sand cores from cast metal statues. Recently, it has also been used to date calcite and loess.