For you metaphysical types, clear quartz is known as the universal crystal. Amethyst is meditative and calming...and was used by the ancient Romans to prevent intoxication. (Yeah, good luck with that.) Rose quartz is the stone of love, kindness, and tolerance. If that's true, every one of us should be walking around with a piece in our pocket.
I'm not a geologist, so it was a lot easier for me to find quartz in one of my local rock shops. (These pictures were taken at a fun shop called Nature's Own.)