Triboluminescence is present in quartz; however, the strength of the phenomenon varies from specimen to specimen. Triboluminescence is well known in sphalerite, fluorite, calcite, muscovite, and many feldspar minerals. Some specimens of common opal produce a bright orange flash.

Test a few specimens yourself. Don’t forget to wear safety glasses, and be aware that this test will scratch your specimens. You will probably discover lots of specimens of various minerals that are triboluminescent. We have found that the flash of light is brightest when we use specimens that are transparent or very translucent. These specimens allow the light to penetrate deeply, making the flash easier to observe.

For years we have observed flashes of light while cutting lapidary rough on a rock saw or shaping it on a diamond wheel. We originally thought this light was incandescence (an emission of light from a hot object), but now we think that at least some of that light was triboluminescence.

Triboluminescence is not a good property to use for mineral identification. Some specimens of a mineral might exhibit the property and other specimens will not.