The Tucson Gem and Mineral Show wraps up Feb. 13. There, you can find pretty much everything — from vintage beads to ancient fossils to meteorites.And that’s a subject Greg Brennecka knows a lot about. Brennecka is a cosmochemist and author of the new book, "Impact: How Rocks from Space Led to Life, Culture and Donkey Kong."The Show spoke with him to learn about his favorite