I went down to the barn last night to crack rock for the upcoming 2022 midwest "Glow Show" in Kentucky. Knowing there would be folks interested in wernerite (A famous LW mineral, very bright) I split a few pieces into saleable chunks. Got a nice 6" specimen, and a huge surprise!
In my experience wernerite is always fluorescent bright yellow LW and a dimmer yellow SW, often with areas of bluish diopside. I admit that I can't be sure I've checked pieces with midwave in the past, but with the new MW flashlights I now check everything. Imagine my shock when I saw this piece! The violet area is strongly fluorescent under MW but shows zero response under LW, and a very minimal response under fluorescent tube SW, none under 255nm flashlight (to be expected - tube lights generate a little MW while the LED is pure 255nm SW).
These pieces are from the original find. Don't think I've noticed this mineral in later pieces, but it certainly makes sense for collectors to examine their pieces with MW. The white light pic shows the clear difference in habit for the violet fluorescing mineral. At first I thought it to be calcite - the cleavage makes sense and it shows a manganese typical BIP (brief intense phosphorescence or flash) when the MW light is removed. But the lack of response under either SW or LW didn't make sense for calcite. Put a drop of acid (vinegar) and examined for bubbles under a microscope - none.
So, for now I'm calling this unknown. Will send samples out for testing.