Osmium is both the densest and the rarest element that you can dig out of the Earth. It's so hard that it's used (as an alloy) in places with constant pressure and wear, like the tips of fountain pens. One single cubic inch of this stuff weighs nearly a pound, and were you to somehow get a cubic foot of it, it would weigh over 1,400 pounds. Good luck with that, though: last year, the entire U.S. osmium production was only 165 pounds.
Amethyst Metaphysical Attributes: Enhances psychic abilities. Excellent for meditation. Aids channeling abilities. Sedative, protective. Enhances feeling of contentment, and a connection to one's spirituality. Stone of peace and strength. Activates crown chakra. Amethyst is the birthstone for February