What are the most interesting or unusual facts you have learned about rocks and minerals?
I think the most interesting thing about minerals is how they are different from other solid substances that are not crystalline, such as glass. For example, light passing through minerals is polarized into two vibration directions. You can block out one of the directions at a time by using a polarizing filter or even some polaroid sunglasses. Glass does not do that to light. Some minerals are able to generate small electric currents by heating them (pyroelectric) or tapping them (pizoelectric). Conversely, if you drive electricity through a pizoelectric cryatal (such as quartz), the mineral vibrates at a regular frequency. That’s why quartz and a small battery are used in a wristwatch — the regular vibration of the quartz can be used to keep time. Electric currents always produce magnetic fields (That’s why the car radio gets static when you go under power lines.). The magnetic field can be “photographed” with the right film. Some very common minerals such as quartz are pizoelectric
