From triboluminescence

And

geocities

Triboluminescence is an optical phenomenon in which light is generated via the breaking of asymmetrical bonds in a crystal when that material is scratched, crushed, or rubbed. Yes, friction causes Triboluminescence, because the phenomenon is basically light from friction. In general, luminescence occurs when energy is input into atoms from heat, friction, electricity, or other sources. The electrons in the atom absorb this energy. The reaction is just the releasing of light.

WintOGreen Lifesavers are naturally fluorescent. The "lightning bolts" give off invisible ultraviolet light -- which cause the fluorescent Lifesavers to give off their own visible fluorescent light. You may have seen something like this in mineral displays under black lights. The black light shines in the ultraviolet, causing the minerals to fluoresce, or glow. In the case of WintOGreen Lifesavers, the fractured sugar crystals generate the ultraviolet -- and the wintergreen molecules absorb it. The result is that, as you chomp your candy, sparks fly.