The desert sultanate of Oman is home to some of the weirdest—and possibly most useful—rocks on earth. The stark Hajar mountains, near the border with Saudi Arabia, contain a chunk of earth’s mantle—a zone that makes up most of earth’s mass, but normally lies inaccessible to humans, far below the surface. Here, though, a sliver of mantle has made its way up to where we can see and touch it. The outcrop has drawn scientists looking for clues to the dynamics of the deep earth; the origins of life; and, most recently, ways to fight climate change.