This is a classic specimen of calcite and aragonite from Worland, WY.
I bought my first UV lamp as a child in the early 60's. It consisted of a mercury bulb, yes bulb, in a small conical housing and maybe put out a watt of UV. Included with the lamp was a book on the fluorescent minerals from Franklin, NJ and a few small mineral specimens. One of those specimens was a piece of calcite and aragonite from Worland. They can be quite beautiful and are very phosphorescent, glowing yellow and blue.