In a sleepy corner of New Hampshire’s White Mountains, 100 miles north of Boston, lies Ruggles Mine, North America’s first mica mine. The yawning open-pit mine overlooks stunning hilltop vistas of red maples and white pines. But when you descend into its 40-foot chasm, the forest disappears. A 15-foot diameter column carved from the rock supports a massive circular entrance. Numerous tunnels branch off the main room, descending deeper and deeper into the mineral-rich rock.

The mine is a veritable treasure trove of minerals: not only layers of mica, but also purple-hued amethyst, feldspar, rose quartz, blood-red garnet, and even rare, colorful uranium minerals like uraninite. First mined commercially in 1805, the site was owned by the Boston-based Ruggles family for more than a century. During that period, sheets of mica from the mine were used as durable yet flexible, heat-resistant glass—perfect for everything from lanterns to stove peepholes.

The pegmatite deposit that makes up the mine formed 300 million years ago. Tectonic plates beneath what would become the eastern edge of the United States collided and folded into each other, creating the Appalachian Mountains. The heat generated from the collision melted lighter bands of minerals within the plates. That liquid then pooled; as it slowly cooled, minerals began to crystallize. Over millions of years, the pegmatite rose six miles to the surface where miners could access the mineral-rich rock.

In 1961, commercial mining at Ruggles Mine came to a halt. Geraldine and Arvid Wahlstrom purchased the historic mine and transformed it into a beloved rockhounding site. Visitors could use pickaxes to collect buckets upon buckets of minerals. Even after her divorce from Arvid, Geraldine continued running the attraction into her 90s. “The children are wonderful,” she told a local newspaper, the Valley News, in a 2016 story on the mine. “Especially the little boys with their buckets full of rocks. They get so excited about them.” After more than 50 years of running the attraction, she was finally ready to retire and put the historic mine up for sale.

A New York-based production company, Exciglow, purchased the mine in 2019 with the hope of reopening it to the public; there’s some uncertainty about whether their plans will ever come to fruition.