Optical phenomena with colliding river rocks

[flatmaster]

Today, I was red-necking it up with some friends in Auburn at the nearby forest. We found an open area on a decent sized creek that was filled with mostly less-than-fist-sized river rock.

After dark, we noticed that when a rock was thrown to the ground (on the other rocks), a small spirt of light would appear. It appeared mostly white, but was perhaps slightly bluish.

I know little about geology, but the rocks were of both light color, and consistent in color.

What's going on here?

 

[Andy Resnick]

Quartz exhibits something called "triboluminescence" (as does wint-o-green life savers)

http://en.wikipedia.org/wiki/Triboluminescence

 

[flatmaster]

That's what I figured. Somehow, an electron gets excited. As the electron returns to a lower state, It ionizes the surrounding air. This ionized air then emits the light.

So there's not much better than that? Sounds like a lot of hand-waving.

 

[pallidin]

I could be wrong, but I think that an electron returning to a lower state does not ionize anything. Rather, the electron emits a photon while returning to a "lower state"