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.
Chalcedony is one of the world`s oldest gemstones. According to archaeologists, humanoids have worn stones, ivory, bone, and certain organic items for personal adornment for about 75,000 years. Which shows its power. Chalcedony prevents from touchiness and melancholy. Worn by many to promote calm and peace. Chalcedony also stimulates creativity. Which is mostly used by astrologers.