Why are rockhounds exploring the shores of Lake Superior after dark, armed with UV flashlights? The answer lies in the glow of Yooperlites. This fascinating discovery has caught the attention of geologists and amateur rock enthusiasts alike, reminiscent of other recent mineralogical finds such as the three new minerals discovered in a unique meteorite.

I have never personally hunted a Yooperlite, but a 2022 article on the subject remains one of the most popular on R&D World two years after it was published. And if I make it to the Upper Peninsula of Michigan, I’ll bring a UV flashlight.

The rocks, which emit a vibrant orange and yellow glow under ultraviolet (UV) light, have become a sensation among rock collectors, geologists, and tourists. The name “Yooperlite,” which Erik Rintamaki coined after discovering that the rocks glowed in 2017, is trademarked. Geological phenomena is not new to R&D World. An article from 2016, for instance, covered the solution to a Yellowstone mystery using Blue Waters supercomputer.

Interest in Yooperlites over time

More recently, search interest in Yooperlites exploded in 2018, but remains strong today based on Google Trends data. Interest tends to surge in the summer months:

Rintamaki, a rock collector from Michigan’s Upper Peninsula, discovered the glowing rocks in June 2017. While searching for agates along the shores of Lake Superior with a UV flashlight, Rintamaki noticed some rocks glowing brightly in different colors. He sent samples to Michigan Technological University and the University of Saskatchewan for analysis, which confirmed that the rocks were syenite with sodalite inclusions.

The glowing rocks of the Upper Peninsula

Yooperlites are primarily composed of sodalite, a mineral with extremely fluorescent properties. While they may appear ordinary in daylight, resembling common granite, they glow when exposed to ultraviolet light. Under UV ray, emitting an orange or yellow glow that seems almost otherworldly. The phenomenon is a result of trace elements within the sodalite that absorb UV light and re-emit it as visible light.

Since their discovery, Yooperlites have sparked a rockhounding surge in Michigan. According to the Michigan Department of Environment, Great Lakes, and Energy, thousands of enthusiasts flock to the region each year, especially in summer months, aiming to uncover the glowing stones.

Yooperlites have also become a subject of scientific interest, with researchers exploring their unique mineral composition and fluorescence mechanisms. The presence of sodalite in the stones was something of a surprise as there was no mention of it in the Mineralogy of Michigan (1976), Mineralogy of Michigan or in Mineralogy of Michigan Update (2013), as the website Yooperlites.com noted.

For those interesting in hunting Yooperlites, Earthly Mission advises using a UV flashlight with a wavelength of 365 nanometers in the dead of night.

The Michigan Department of Environment, Great Lakes, and Energy reminds rock hunters that collecting stones from national parks or lakeshores is prohibited, and permission is required for collection on private land. Public beaches have limits on how much material can be taken.

Related links

• Study Suggests Water May Exist in Earth’s Lower Mantle: Learn about a geological analysis that helps us understand our planet’s composition.
• Researchers Find New Way to Estimate Magma Beneath Yellowstone Supervolcano: Explore new research methodologies in geology, similar to the interest sparked by Yooperlites.
• Geological Society of America: Learn more about the organizations conducting continuous geological research.
• Three New Minerals Discovered in Unique Meteorite: Read about other mineralogical finds (article is form 2017).
• Blue Waters Solves Yellowstone Mystery With Assist From Stampede: Learn about another geological phenomenon solved using advanced techn.