I have already read this question about triboluminescence but it doesn't really cover my question.
I am trying to understand what causes quartz crystals to glow when mechanical pressure is applied to them. (Here is a short video of the effect I'm talking about). Most of what I have read has stated that triboluminescence is caused by separation of charge when a crystal is broken leading to ionization of nitrogen in the air (i.e. wintergreen lifesavers). For quartz, this doesn't seem to be the case. There is no (visible) fracturing and I can rub two quartz crystals together repeatedly to get the effect over and over. Originally, I thought that the mechanical pressure provided some sort of activation energy that allowed electrons to jump bands but I can't seem to find anything to support that in my solid state textbook or in research articles.
So, what is the mechanism that produces light in triboluminescent quartz?
Bonus points if you can point me towards a textbook or article on the subject. Everything I've found has been rather lacking.
