An Emberlite from Michigan. These stones contain a fluorescent form of the mineral sodalite.
You will need a proper 365nm UV light for viewing this stone! Here are a couple of my recommendations:
This is a great entry level 365nm UV light, perfect for revealing the fluorescent sodalite in this specimen: CLICK HERE
This is an excellent, extremely powerful 365nm UV light, perfect for field collecting or viewing this specimen: CLICK HERE