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triboluminescence was named in 750 BC!?
it is an chemical property by giving off the glow.
Triboluminescence is an optical phenomenon, consequently is a physical property.
Triboluminescence is an optical phenomenon when certain types of crystals are pulled, ripped, crunched, or rubbed they generate flashes of light.
The exact cause and mechanism of this phenomenon is still unknown.
Because of the triboluminescence.
Triboluminescence