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This greenish sodalite (hackmanite) is very tenebrescent. Uranyl activated greens make for an interesting pattern.
Greenland produces some of the most tenebrescent sodalite found anywhere. These pieces darken when exposed to SW UV in seconds, and fade just as rapidly upon exposure to a bright white light. This process can be repeated over and over. They are also perhaps the most fluorescent of the sodalites found around the world - a bright yel/orange under LW and SW, but under SW as the tenebrescence sets it, the color darkens to a rusty orange. Photos show SW and LW, as well as the tenebrescence. The animation shows this color change before/after UVC.
365nm UV light is often called "blacklight". Before the advent of longwave UV LEDs, blacklight fluorescent tubes, (the kinds used in hippie days to light up psychedelic posters) were the standard longwave UV light for our hobby. They were not very powerful but they did light a large area.
Enter 365nm UV LEDs
First, an animation showing the difference between the UV flashlight we recommend (365nm filtered UV flashlight) versus unfiltered 395nm UV flashlights we see many folks carrying around at shows. So. much. visible purple light. We selected a bunch of rocks as a demonstration. Took pictures of them under his flashlight without the filter and then with the filter.
A major component of rock collecting (for us) is simply getting out in nature. A buddy dragged us out to a very remote area here in middle Tennessee to hunt for fluorescent green agate. Since we consider ourselves pure "Glow Hounds" we weren't anticipating any glow rocks, just the beauty of the area, but we brought our UV lights anyway.
