Minerals & Gemstone 480x104
Minerals & Gemstone 480x104


Luminescence describes any circumstance that causes a mineral to give off light. Fluorescence is one form of luminescence, in which fluorescent minerals glow in ultraviolet light. Triboluminescence and thermoluminescence are two additional forms of luminescence. Triboluminescent minerals gives off yellow or orange flashes when struck, and thermoluminescent minerals gives off a glowing light when heated. Only few minerals are triboluminescent or thermoluminescent, so this property is not very useful for identification. It is also impractical to heat or strike minerals to see if they exhibit any of these properties. However, simple testing for thermoluminescence can be done by putting a specimen in the flame of a lighter for a short time in a dark area. If it glows for a few seconds after the flame is removed, it is thermoluminescent. This test should only be conducted on extra, unwanted specimens, for heating a specimen in such a way may permanently blacken it.

To test for triboluminescence, strike the specimen with a steel file or other tough substance in a dark area and see if sparks fly out. This test should also only be conducted on extra specimens, since the steel file will scratch most minerals.

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