Have you ever tried this? If not, it is a very illuminating scientific experiment you can do at home. Plus, it freshens your breath. Here's how:
- Buy some regular Certs or Wint-O-Green Lifesavers
- Get a friend to act as your assistant
- Go to a completely dark place, like a closet at night with your assistant
- Wait for your eyes to adjust to the dark
- Place a Cert in your mouth and bite down on it with your mouth open so your assistant can see
If you did everything right, you should be able to see a faint blue spark when the Cert breaks up between your teeth. If your assistant didn't see the spark, try again. It really does work. Have your assistant eat a Cert or two so you can see the magical blue spark too.
What you see when you bite into a Cert in the dark is a manifestation of what is called "triboluminescence" - the mechanical generation of light. That is to say, some substances become luminous when scratched, crushed, or rubbed. Several minerals exhibit this property, fluorite (chemically this mineral is calcium fluoride) being one.
While the mechanism of light generation is not exactly clear, current thought on the matter is that when a hard crystalline material is broken into pieces (upon mechanical fracture), charge is separated momentarily in the material and light is produced upon discharge, or recombination, of the separated charges. | 
