Rocks......
Well not exactly rocks but....
So far I've got hmm...
Blue, Yellow, and Clear Topaz, Garnets, Star Sapphires, Star Rubies, Sapphires, Emerald, Quartz Crystals, Amethyst, Citrine, Hiddenite, Rose Quartz crystals, Amazonite, and a few others I can't think of off hand.
Job I had until it closed down required lots of travel, on weekends I had to work my GF, who worked there as well and wrote my route schedule, would set it up so that I went into areas that had public Gem Mines, of course since she wasn't required to work weekends she always rode along with me. Which makes me wonder, how many other people here have a GF that knows how to change the Transmission in washing machine.......
Other than Rocks, I've been building a collection of Piers Anthony books (Xanth Series), along with snapping up old D&D books from the late 70's as I can find them. Actually got lucky and picked up a first print edition of the original Monster Manual for $8 at a used book store, only ones I could find on Amazon at the time started at around $500 (art was changed after the first printing because up-tight conservatives complained about the anatomical detail of some of the art making them pretty rare). I consider that a lucky find, I also grab up Novels and Novellas published with the TSR label and not WoTC, the variety was broader, and seriously everything about AD&D that's been released under WoTC's ownership has sucked. I mainly try and get Forgotten Realms, Dark Sun and Ravenloft series books, primarily the latter two due to trouble finding them, many of the Dragonlance setting books are still in print and I have copies of the most popular ones. The Last time we moved I realized I had more books than clothes.....