Glowing rocks in Michigan? What to know about 'Yooperlites'

KylaSci/Tech2025-06-293940

Most people do their rock hunting during the day, but you can't find "Yooperlites" until the sun goes down.

Yooperlites are rocks that fluoresce in the dark under ultraviolet light. They became known when an Upper Peninsula resident discovered them in 2017,according to the Michigan Department of Environment, Great Lakes and Energy.

Spring is the best time to search for Yooperlites and other rocks, according to Pure Michigan, because winter ice moved beach sand and stones around, leaving newly unearthed stones along Lake Superior's shoreline to be discovered.

Throughout the year, the best time to seek Yooperlites and other stones is after a storm, when waves have disrupted and uncovered new rocks.

Florescent sodalite lights up under UV light

Here's what to know about the rock that is found in the Upper Peninsula along Lake Superior:

What is a Yooperlite?

Yooperlites are a variety of sodalite-rich syenite found in the Upper Peninsula of Michigan.

Syenite is a coarse-grained, plutonic (intrusive) igneous rock that primarily consists of the minerals feldspar, typically orthoclase feldspar, and often includes smaller amounts of other minerals such as hornblende, mica or amphibole. Unlike granite, which is another common intrusive igneous rock, syenite contains minimal to no quartz, Geology Science said.

Sodalite is a deep blue to blue-violet mineral best known for its use in jewelry, sculpture, and decorative stonework. Sodalite forms in igneous rocks that crystallized from sodium-rich, silica-poor magmas. That’s how it got its name — soda and lithos, or “sodium stone," according to Rock Your World gem and art gallery.

In normal light, a Yooperlite looks like granite. Sodalite replaces quartz, so the larger the mineral size, the brighter the shine, EGLE said. There are roughly five classes of Yooperlites:

Gemmy(mostly sodalite or large sodalite crystal, the entire specimen glows orange)

SnowflakeorFlower(similar to snowflake obsidian, large blotches on the surface that look like snowflakes, but crystal glow does not penetrate into the interior)

Striated(sodalite fills cracks in the rock matrix, so appears as orange lines or veins)

Spray Paint(tiny crystal droplets scattered around the surface)

Galaxy(larger crystals than spray paint that are dispersed in the rock that glow like the night sky, crystals penetrate the matrix)

Where can I find Yooperlite rocks?

The rocks can be found in different areas throughout Michigan, but are most likely to be found in the Upper Peninsula along Lake Superior, often on beaches near Grand Marais and in the Keweenaw Peninsula.

Yooperlitescan be found as loose pebbles and cobbles along many Lake Superior beaches and even in some inland gravel pits. The stones are derived from igneous rocks nearMarathon, Ontario,known as the Coldwell Alkaline Complex and were transported into Michigan by glaciers during periods of continental glaciation.

How to search for them:

Start with a beach that has stones.

Get a good UV light (365 wavelength).

Wear safety glasses with UV protection.

Take along a garden tine rake to move the deposited gravel around or to reach out into the water. Yooperlites may not shine on all surfaces, so moving stones around will increase your chance of seeing them.

Be strategic: Use a sweeping side-to-side motion for better coverage and light angle about 6 to 8 feet in front.

Walk at a normal pace and shine the light with a sweeping motion.