Yooperlites are fluorescent sodalite-bearing rocks found along the shores of the Great Lakes in Michigan’s Upper Peninsula and along Lake Superior. Collecting fluorescent rocks has grown in popularity; understanding what makes minerals glow under ultraviolet light is just as important as knowing where to find them.
Key Takeaways
- Yooperlites are fluorescent sodalite-bearing rocks found along the shores of Lake Superior and parts of Michigan’s Upper Peninsula.
- Erik Rintamaki discovered and named Yooperlites in 2017 while searching for rocks with a UV flashlight along the Lake Superior shoreline.
- The rocks glow bright orange or yellow under ultraviolet light because they contain fluorescent sodalite.
- Michigan Technological University analyzed Yooperlites and confirmed they are syenite rocks containing fluorescent sodalite.
- Yooperlite hunting has become a popular rockhounding activity, attracting collectors, educators, geologists, and visitors to the Great Lakes region.
- Scientists believe the rocks originated in Canada and were transported to Michigan by glaciers during the Ice Age.
Discovering and Naming Yooperlites
Erik Rintamaki of Michigan’s Upper Peninsula first spotted something unfamiliar and intriguing along the shores of Lake Superior under the setting sun and evening sky.
Erik named these fluorescent sodalites “Yooperlites.” They quickly caught the attention of geologists, mineralogists, rockhounds, educators, and Upper Peninsula visitors.
The origin of the name “Yooperlites” is the abated abbreviation of “U.P.” for Michigan’s Upper Peninsula. “Yoopers” are the area’s colloquial citizenry. “Lite” refers to the rock’s fluorescent properties from sodalite.
Since making the discovery, Erik has spent quite a bit of time talking about Yooperlites and leading rockhounding tours. As a dedicated rockhound whose hobby is also his business, a good day rockhounding is a good day all around.
Beachcombing Lake Superior Shores
Several years later, my wife, Brenda, and I had the good fortune of hearing Erik speak about Yooperlites during our travels in September 2018. Early in our autumn travels, we went to the Upper Peninsula of Michigan, one of our favorite rockhounding areas. A few years earlier, we successfully explored the western region of the U.P., so this time around, we mapped out the eastern region to explore with hopes of finding prized Lake Superior agates.
Beyond its scenic shorelines, the region is rich in mineral heritage. Itserved as the United States’ primary copper supplier for more than a century, producing an estimated 10.5 billion pounds
We stayed at Muskallonge Lake State Park, located on the U.P.’s northeast shores near Newberry, Michigan. The park ranger let us know that the annual Rock On with Lake Superior Agates rock show had just started. So, we set up our campsite and went to the show.
Rock On! A Lake Superior Agate Show Surprise
Educational demonstrations and rock and mineral presentations filled the two-day event. Of course, tables of Lake Superior agates and other local mineral specimens were there, too. There was something for all ages.
One of the presentations that especially caught my attention was Erik’s Yooperlite display. During the show, Erik began sharing the story of the discovery made on the shores of Lake Superior.
We listened intently and examined the amazing fluorescent display. We were intrigued by the display and decided to change our travel plans and stay for a few more days.
The next morning, I headed directly to the area where Erik was presenting. We talked for a few hours, and he explained more about his discovery. He has been a rock-collecting enthusiast since childhood. It began with his dad taking him rock collecting when he was very young. Needless to say, he never lost his passion for collecting or his curiosity about minerals.
How the Discovery of Yooperlites Created Opportunity
Necessity is the mother of innovation, and in Erik’s case, it may be the mother of discovery, too. In addition to being a collector and dealer of Lake Superior agates for years, he also teaches others how to find the elusive U.P. treasures.
In his quest to become more successful with his knowledge of agates, his curiosity caused him to see if agates would fluoresce. One such night in June of 2017, with an inexpensive 3-LED UV longwave flashlight, he went rock hunting around 4 a.m. and discovered a rock that looked like a hot lava ball. He was “excited beyond containment and wondered what it was,” Erik explained.
Discovering two small specimens hooked him. Erik upgraded his equipment to include a 100 LED UV flashlight, which significantly increased his discoveries. This led him to begin working with a manufacturing company to produce a cost-efficient UV flashlight to help people locate Yooperlites.
Building Scientific and Public Interest in Yooperlites
As Erik would learn, his discovery of fluorescent sodalite would bring forth great interest from a variety of people.
One example of this came about in January of 2018, when the online sale of some of Erik’s Yooperlites attracted the attention of geologist Raymond Laughlin and Shawn M. Carlson, a geologist and mineralogist, respectively, both from Michigan. They purchased some of Erik’s rocks and began to technically analyze the specimens.
With access to the geological laboratory at Michigan Technological University (MTU) in Houghton, Michigan, the technical assessment of the Yooperlite mineral was underway. I was intrigued to learn of the connection to MTU because, during our first trip to the Upper Peninsula, we stopped at the A. E. Seaman Mineral Museum, which is located on the campus grounds at MTU. It is one of the premier collegiate mineral museums in the United States and is very much worth visiting.
Enjoy a short video filmed by Erik as he hunted for Yooperlites along the shores of Lake Superior
What Makes Yooperlites Glow?
The following is an excerpt of the Yooperlite mineral analysis from MTU (used with permission from Tony Nikischer, publisher of Mineral News, info@excaliburmineral.com).
Preliminary SEM/EDS analyses conducted at Michigan Technological University showed only Na, Al, Si, Cl, and O in the mineral’s spectrum.
Sulfur was sought but not noted with EDS (below detection limits) but was detected by follow-up EMP/WDS, which yielded a composition of: 36.47 wt.% SiO2, 30.84 wt.% Al2O3, 25.39 wt.% Na2O, 0.31 wt.% FeO, 0.05 wt.% K2O, 7.02 wt.% Cl, and 0.11 wt.% SO3 (average of three very similar analyses).
Microscopic studies were conducted using a Kyowa SDZ-P binocular stereozoom microscope and a Kyowa ME-POL2 petrographic and ore microscope equipped with a Super spindle stage.
EDS spectra were obtained at Michigan Technological University on a JEOL 6400 tungsten-source SEM equipped with a 4pi Analysis (Inc.) ultrathin window EDS detector and operated at 20 kV, using standards from Astimex Standards (Ltd).
Yooperlites Explained: Composition and Origin
Yooperlite, which this analysis has shown, is a syenite clast containing fluorescent sodalite, and at this point, is reportedly specific to the shores of Lake Superior in Chippewa and Luce Counties and in the Keweenaw Peninsula. It is the first verified and documented sodalite from the state of Michigan.
Geologically, the rock likely formed in Canada before a glacier carried it from the Canadian Shield (Laurentian Plateau) to Michigan.
Because sodalite is a common mineral, the technical analysis shows nothing new. What makes this unique is that it is the first time sodalite was discovered in Michigan.
From an earth science and rock-collecting perspective, it is a great discovery. It is the type of discovery that creates a rudimentary basis for sparking interest in earth sciences for young and old alike.
Why Yooperlites Are Important to Rockhounds
Few modern mineral discoveries have captured the imagination of rockhounds quite like Yooperlites. While sodalite itself is a well-known mineral, the discovery of fluorescent sodalite-bearing rocks along the shores of Lake Superior created a new collecting phenomenon in Michigan’s Upper Peninsula.
Part of the appeal is the excitement of the hunt. Armed with a UV flashlight, collectors can walk beaches after dark and watch ordinary-looking rocks suddenly glow bright orange or yellow. This unique experience has introduced many newcomers to rock collecting while giving experienced rockhounds a new challenge to pursue.
Beyond their visual appeal, Yooperlites have helped spark greater interest in fluorescent minerals, geology, and Great Lakes rockhounding. Their discovery demonstrates that even in well-explored regions, surprising finds are still possible. For many collectors, Yooperlites serve as a reminder that curiosity, observation, and persistence remain some of the most important tools in rock collecting.
Finding Yooperlites Along Lake Superior
Yooperlite hunting has become one of the most popular forms of rockhounding in Michigan’s Upper Peninsula. These fluorescent sodalite-bearing rocks are most often found along Lake Superior shorelines after dark when viewed with a longwave ultraviolet (UV) flashlight. Popular collecting areas include public beaches in Chippewa County, Luce County, and parts of the Keweenaw Peninsula.
For the best results, search after sunset and scan the beach with a UV light. Under ultraviolet illumination, the sodalite within Yooperlites glows bright orange or yellow against the darker surrounding rock, making specimens much easier to spot. As with all rock collecting, be sure to verify local regulations and collect responsibly on public lands and shorelines.
Yooperlite FAQs
What are Yooperlites?
Yooperlites are syenite rocks containing fluorescent sodalite. When viewed under a UV flashlight, the sodalite glows bright orange or yellow.
Where can you find Yooperlites?
Most Yooperlites are found along the shores of Lake Superior in Michigan’s Upper Peninsula, particularly in Chippewa County, Luce County, and the Keweenaw Peninsula.
Why do Yooperlites glow?
The glow comes from fluorescent sodalite within the rock. Ultraviolet light excites the mineral, causing it to emit visible light.
Do you need a UV flashlight to find Yooperlites?
Yes. While Yooperlites can be seen during daylight, a longwave UV flashlight is typically needed to identify them because of their fluorescent glow.
This two-part series by Wayne Peterson about Yooperlites appeared in a previous issue of Rock & Gem magazine. Click here to subscribe.
