Recently, we packed up our things and headed up to Michigan. I originally had hoped to go to the Upper Peninsula to look for a type of rock that is called syenite or Yooperlite's as they are commonly called in Michigan. Syenite is a coarse-grained intrusive igneous rock formed when molten lava cooled slowly under the Earth’s surface. It has a general composition like granite. Not all syenite glows in the dark. These particular rocks were probably formed in Lake Algonquin Ontario and washed up on the shores of Lake Superior many years later due to glacial activity.
Fluorescence is light that is absorbed in the UV spectrum which can not be seen with the naked eye. The rocks absorb this light and then emit it in a longer wavelength. The electrons in the rocks get "excited" by the UV light. This scrambling of electrons releases light waves in the visible spectrum. "Yooperlites react at about 395nm so if you go to look for them find a UV light that display in this range. The Convoy C8 + 365 nm UV LED Flashlight is a good one.
You can also use your handy UV Flashlight to detect cat urine!! I used it in the bathroom and found all kinds of interesting creatures...
We did find a few Petoskey stones near Travers City. That was fun (but cold).