Glass Buttes is a remote cluster of volcanic mountains in Oregon’s high desert, notable for vast and varied obsidian deposits formed millions of years ago in ancient silicic volcanoes. For thousands of years, Native Americans quarried obsidian here for tools and weapons, and material from the buttes spread widely in trade across the Pacific Northwest. In the early 20th century, scattered homesteaders and prospectors came to the area, but most settlements were abandoned because of water shortages and wartime economic pressures. Later surveys identified several kinds of natural glass, and mercury was mined here until falling prices ended production. Today the isolated buttes remain popular with rock collectors and other visitors.