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A piece of nicely tenebrescent hackmanite from Afghanistan.These sodalite hackmanite specimens also display an incredible phosphorescence.
Hackmanite is a pink to greyish-white, lavender to white variety of sodalite. Sulfur replaces some of the chlorine atoms in the sodalite structure. The sulfur content can give sodalite reversible photochromism or tenebrescence. The fluorescent community reserves the name hackmanite for tenebrescent sodalites.
Below is an excerpt from the Journal of the Fluorescent Mineral Society, Volume 39 - “Hackmanite all fluoresce orange in longwave UV light. All of the hackmanites have strong and long-lasting white afterglow after exposure to shortwave UV light. Strong, long-lasting dark purple tenebrescence is associated with these hackmanite specimens. The tenebrescence is very long lasting. It takes several hours under a strong halogen light to reverse the tenebrescence.”
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.
