The Bon Ami Mine’s deposits of the mineral hyalite glow fluorescent green under ultraviolet light
It’s 8 p.m. on a windy autumn night, and I’m walking down a dirt pathway to the entrance of the Bon Ami Mine in Little Switzerland, North Carolina, located about 50 miles northeast of Asheville. Decades ago, the mine was fully operational and prized for its abundance of gems and minerals like feldspar, mica and quartz, but today it’s part of Emerald Village, a popular mining attraction for rock hounds and anyone who’s interested in learning more about the Blue Ridge Mountains’ mining history. Glass Sand
While Emerald Village is chock full of activities for all ages, including panning for riches like emeralds and garnets, and exploring its rambling, multi-story mining museum that contains mineral specimens found onsite, I’m here on this seasonally chilly Saturday night to experience its Black Light Mine Tour. The exclusive event is held only ten times a year and is the best way to see the mine’s towering walls and ceiling, which are encrusted with large deposits of hyalite, a form of opal known for its glass-like transparency. When viewed under ultraviolet light, the normally colorless gemstone glows a brilliant fluorescent green.
Hyalite’s intoxicating glow, which immediately calls to mind kryptonite from the Superman comic book series, is due to the gemstone’s trace amounts of uranium, a chemical element that glows when exposed to ultraviolet light. Uranium was once a popular material in glassmaking simply because it fluoresces under UV light. “The UV excites the electrons above the ground state and gives off photons as the electrons transition back to the ground state,” an article in Collectors Weekly explains. “The fluorescence is just an inherent property of the uranyl compound in the glass.”
“When you look at hyalite in the daylight, it’s colorless and often has a bubbly appearance,” says Jeff Post, a curator of the mineral and gem collection at Smithsonian’s National Museum of Natural History and a research mineralogist. “It’s a clear layer that can be found on the top of rocks. It fluoresces bright green under black light due to the trace amounts of uranium contained within the opal layer.”
The more uranium a hyalite deposit contains, the brighter it glows. I wanted to see the light show for myself, and Bon Ami Mine is one of only two mines in the United States that are open to the public and offer black light tours (the other one is located in Franklin, New Jersey, at the Sterling Hill Mining Museum, which contains a display of 100 different fluorescent mineral specimens.)
The tour at Bon Ami begins with a quick overview of the history of the mine, which opened in the early 1930s by the Whitehall Company, the mining division of Bon Ami, a company that has been producing cleaning products since 1886. The mine is one of more than a dozen in the region that make up the McKinney Group of mines and is rich in feldspar, a category of aluminosilicate minerals that also happens to be the most commonly found mineral group on the planet. (Sixty percent Earth’s crust is made up of feldspar, according to the U.S. Geological Survey.) Using chisels and hammers, miners would collect the abrasive material by hand. Miners found that the feldspar would inadvertently polish their shovels as they dug, confirming it to be the perfect ingredient to make Bon Ami’s popular polishing powder, which is still manufactured today.
Fast forward nearly a century, and the mine is now owned by Alan Schabilion, whose father, Robert, purchased Bon Ami along with the adjacent Big Deal Mine in 1979 after the Whitehall Company pulled out its operations there in the 1960s, as the mining industry shifted from underground mining to lower-grade deposits that are easier to access. By 1980, the Schabilion family was giving public tours of the picturesque property, which is punctuated by a waterfall, offering people, for a small fee, buckets and chisels to try their hands at mining.
In 2006, when Alan and his wife took over the property from Robert, they already knew it was rich in hyalite and dozens of other gems and minerals. About 15 years ago, thanks to better quality high-powered portable UV lights, the couple waited until nightfall one evening and, with lights in hand, entered the Bon Ami Mine. What they saw next was out of this world and led them to begin offering the blacklight tours about ten years ago.
“We were in complete awe,” Schabilion tells me. “We expected to find something, but found more than we thought we would, discovering hyalite opal high up in the mine’s 50-foot-tall ceilings that still responded to the light. We went and bought even more powerful black lights and it was then that we knew we wanted to show these minerals off to the public.”
As Schabilion speaks, I stare up at the mine’s towering ceiling, with its jagged striations of hyalite that remain invisible but come alive every time he sweeps past it with his handheld light. Along with his staff, which contains several family members, including his sister and a few of his children and grandchildren, Schabilion leads the mine’s black light tours, which draw about 1,000 tourists from around the world each year. (About 25,000 people visit Emerald Village each year.) The team relies on a dozen portable short-wave UV lights that produce 195 watts each to illuminate the roughly 100-foot-long mine. (An additional 150 feet of the mine is inaccessible since it resides underwater.)
While Bon Ami is shallower and more cavern-like than coal mines, which are known for their labyrinths of endless tunnels that burrow underground, the open space is actually preferable, since its ample height helps accentuate how much hyalite really exists in its walls. During the hour-long tour, I’m able to get close up to the rock walls and see them from a perspective that’s hidden to the naked eye during daylight hours and without the aid of a black light.
“We want people to be as amazed as we are, and to appreciate the beauty found underground and in hard-to-reach places like this mine,” Schabilion says. “It’s incredible to think that there are plenty of spots in this area that haven’t been explored yet and all the deposits waiting to be discovered.”
Emerald Village is open from April through October. Check out this schedule for black light mine tours in 2022.
Jennifer Nalewicki is a Brooklyn-based journalist. Her articles have been published in The New York Times, Scientific American, Popular Mechanics, United Hemispheres and more. You can find more of her work at her website.