The search for dark matter is an all-encompassing one, and that’s understandable—after all, 85 percent of reality is made up of the stuff, and you’ve never seen it. That’s a fair reason to be concerned with finding it as soon as possible. In their search, scientists have probed the stars in search of potentially high concentrations of axions (a leading dark matter candidate), hunted for the elusive particle in Earth’s atmosphere, and even delved deep underground in search of any hints. Now, scientists from Virginia Tech and other international universities are leading another kind of search with a decidedly low-tech focus: really old rocks.