Rub our Flash Rocks together to see a totally natural piezoelectric rock show! They'll glow internally and emit a distinctive odor! If you're lucky... someday soon you will be holding electric potential in your hands, so you can see for yourself. Flash rocks - aka quartz - are one of the few minerals with piezoelectric proprieties. So, when subjected to mechanical stress, these two little rocks generate an electrical charge. Just place a rock in each hand, and forcefully rub the rocks together. To see the glowing electrical effect fully, you should do this in a darkened room. Also, note the distinctive odor given off by the frictions.