Frey Scientific Fluorescent Light Set, 15 pcs. The center stone creates the bright black light effect you can expect. Some of the other stones glow faintly, while others don't glow at all, unless you might have a shortwave UV source. However, after walking through the entire stone store on Hilton Head Island with a UV flashlight that didn't illuminate anything, I'm glad I have some fluorescent minerals. The UV photo was a 5 second exposure lit with a 4w longwave UV lamp with a filter approximately 18 inches above the rocks. The blue stone at the bottom of the penultimate column actually appeared a duller purple to the eye.