Yooperlites, also known as Glowdalites, are luminescent stones found in the Upper Peninsula of Michigan. They are a type of syenite rock with a high concentration of sodalite, a mineral that glows under ultraviolet (UV) light. Yooperlites come in various colors, including orange, yellow, green, and blue.
Yooperlites were first discovered in 2017 by Erik Rintamaki, a gem-hunting expert from Michigan. At that time, Rintamaki was searching for rocks along the shores of Lake Superior at night using a UV flashlight to illuminate the stones. He noticed some rocks glowing brilliantly in various colors.
He had never seen anything like them before and decided to send some of his discoveries to Michigan Technological University and the University of Saskatchewan for analysis. They confirmed that these rocks were syenite with sodalite impurities and could have formed around 1.1 billion years ago during a volcanic activity period.
Researchers from Michigan Technological University and the University of Saskatchewan studied and analyzed these stones to understand their composition and origin. In a publication in Mineral News, they announced that these stones are merely syenite with sodalite inclusions. They contain several minerals such as microcline feldspar, sodalite, nepherline, cancrinite, and pyroxene, all responsible for giving Yooperlite its special glow when exposed to UV light.
Rintamaki decided to name them Yooperlites, after the slang term for people living in the Upper Peninsula of Michigan (U.P.), also known as Yoopers. He even trademarked the name and began selling the stones online and at exhibitions. He also organized tours and workshops to teach people how to find and identify Yooperlites. His discovery sparked immense interest and excitement in the rockhounding community and media.
But why do these rocks glow? As noted earlier, it is because they contain a high concentration of sodalite, a blue mineral belonging to the silicate group, typically found in igneous rocks like syenite and granite, formed from molten magma. Yooperlites appear quite ordinary in daylight, but when you shine UV light on them, they reveal their hidden beauty.
Yooperlites can primarily be found along the shores of Lake Superior in Michigan, particularly in areas such as Grand Marais, Paradise, Whitefish Point, and Brimley. They can also be found inland in certain areas where glacial deposits have carried them. According to information from Earthlymission, they can also be found in most of the Great Lakes region of the United States and even scattered in various locations around the world. However, finding them is not easy as they blend in with other types of rocks and gravel.
To the naked eye, these stones — composed of oxygen, silicon, chlorine, sodium, and aluminum — appear bluish-gray with white streaks. Thus, they are often used in mosaic products, but when placed under longwave UV light, sodalite will glow, revealing a mesmerizing pattern of red and yellow veins.
The best way to find Yooperlites is to use a UV flashlight with a wavelength of 365 nanometers (nm), which is the optimal frequency for achieving sodalite fluorescence. You should also search at night or in dark conditions, as daylight can diminish their glow. It is advisable to wear protective glasses and gloves when handling UV sources, as they can be harmful to your eyes and skin.
When you discover a glowing rock, you can pick it up and examine it more closely. You may also use a magnifying glass or loupe to see the details of the sodalite crystals. You might be surprised by the variety of colors and patterns that Yooperlites display under UV light.
Yooperlites were formed through a combination of volcanic eruptions and glacial movement. They formed about a billion years ago during a dramatic geological period when North America attempted to split apart. A rift formed, leading to unimaginable volcanic eruptions and 360,000 cubic miles of lava — an eruption that created an ocean of lava over 1,700 feet deep. Despite this activity, the rift ultimately failed to divide North America, largely remaining beneath Lake Superior today. The last Ice Age, approximately 10,000 years ago, swept these glowing stones southward, leaving behind the Yooperlite chunks we find today.
However, be careful as collecting stones in national parks or national lakeshores is strictly prohibited by law. You also cannot collect and keep Yooperlites from private land without the landowner’s permission. The same applies to historical sites such as parks or designated conservation areas.
