By Adam Kelliher
The short answer: yooperlite is a trade name, not a new mineral. It's a grey syenite rock from the Lake Superior shore of Michigan's Upper Peninsula that contains fluorescent sodalite, which glows bright orange-yellow under a longwave UV light.[1][2]
In daylight a yooperlite looks like any other grey beach pebble. Put a UV flashlight on it at night and it lights up with orange spots and swirls. That trick is why they've become one of the most asked-about rocks we sell.
Where the name comes from
People from Michigan's Upper Peninsula (the "U.P.") are called Yoopers. In June 2017, Erik Rintamaki took an inexpensive longwave UV flashlight to a Lake Superior beach before dawn and found glowing pebbles. He began selling them as "yooperlites".[1]
What's actually in it
Researchers from Michigan Tech and Washington State examined the stones and confirmed the glowing mineral is sodalite, in a syenite host rock. They reported it as the first verified sodalite from Michigan.[1] Mindat lists "yooperlite" as a synonym of sodalite-syenite.[2]
Why it glows
Sodalite, including the sulphur-bearing variety called hackmanite, can fluoresce orange under longwave UV.[1][3] The UV is invisible to us, and the mineral re-emits some of that energy as visible light. When the UV switches off, the glow stops.
How did it get to Michigan?
The Ontario Geological Survey notes the likely bedrock source is the Coldwell Alkaline Complex on the north shore of Lake Superior, where fluorescent hackmanite occurs in syenite. Glaciers probably carried the pieces south, and waves rounded them.[3]
Seeing one glow
You need a longwave UV light, ideally around 365 nm. A filtered light shows the glow much better than a cheap purple-looking one. Look in the dark, and never shine a UV light into anyone's eyes.[4] Our Convoy S2 UV flashlight is a good one. Tomorrow's post covers UV lights for your whole collection.
We stock yooperlites from Michigan and plenty of other fluorescent minerals.
See what's new: browse our newest arrivals for the latest pieces added to the shop.
Sources
- Laughlin, R., Olds, T.A. and Mills, O.P. (Michigan Technological University and Washington State University), A New Find of Fluorescent Sodalite (the 2018 yooperlite study).
- Mindat.org: Yooperlite, a synonym of sodalite-syenite.
- Ontario Geological Survey, Ontario Mineral Inventory record MDI000000002296, Yooperlite Source (Coldwell Alkaline Complex).
- Fluorescent Mineral Society: longwave and shortwave UV basics and safety.