Wednesday, June 6, 2018


When writing my recent blog post on Fluorite click here, I was captivated by the amazing colors when I put a cab of it under fluorescent light!  Thought I'd learn more about it and make it a new blog topic. So here it is!

Multi-colored Fluorite!


I'm one of those who "ooh'd" and "ahh'd" at fluorescent displays at rock shows, and I'd even purchased a UV lamp to check out the colors in some of my rocks, but I'd never thought much about how that "fluorescent" thing happened.

I've always said that being a writer gives me an opportunity to indulge my own curiosity. So I started researching and discovered some fascinating facts.

It seems that when a UV (ultraviolet aka electromagnetic) light is shined on certain minerals, they absorb it. Then they immediately glow or shine some of that light back out on a different wavelength. The process of the mineral changing the wave of the light is what creates the colors we see--as long as we're doing it in a dark place. Visible (white) light can make it harder, if not impossible to see the fluorescent colors.


Natural light

To me, one of the most spectacular colors comes from putting a piece of ruby and fuchsite under the uv lamps.  As a lapidary rock, it can be challenging to work with since the two minerals can be very different hardnesses.

You can find beads or chunks of it at rock shows. I love the old-fashioned beauty of the red ruby and green fuchsite with touches of white.

Same bead under long wave uv light

The ruby itself isn't likely to be gem quality, but that doesn't matter in this situation. When it goes under uv lamps, it looks like it has a fire within.

This particular bead shown so brightly that I had a hard time getting a clear photo of it because the brightness overwhelmed the filters on my camera.


The UV light source you choose will have a big impact on the fluorescence you see.

There are two common types: long wave (LW) and short wave (SW). This adds layers of confusion for people like me who are new to understanding fluorescent minerals.  For example:

     * A mineral may fluoresce the same color under either LW or SW light.
     * It may only fluoresce under one or the other.
     * It may fluoresce different colors under the different wave lengths.
     * The same mineral may fluoresce different colors if it came from different regions. According to, "Calcite may fluoresce red, orange, yellow, white, and green, but it will always fluoresce red at Franklin, New Jersey, and bluish-white at Terlingua, Texas."

This image of Hackamaite taken under long wave lights looks like it has a fire inside!


Never, ever look directly into the lit portion of a uv light source. It may not look all that menacing, but it can permanently damage your eyes! In addition, don't let your skin be exposed to the light for long periods of time; you can get a sunburn (remember, the sun sends ultraviolet light too) or long-term skin problems.

This Willemite stone above is shown at different angles. The green is how it fluoresces under long wave light.


When I started researching this post, I already had a 9 Watt UV Shortwave box I'd purchased from Way Too Cool Click here. It was fun, but not completely satisfying compared to the fluorescent rocks I've seen at rock shows.  I got in touch with Bill Gardner Click here the owner and purchased at Longwave flashlight, and now I'm having fun comparing different specimens under the different lights. For example:

This Calcite is photographed in daylight. Shiny, but not much wow factor.





This blue is what happened when I photographed the same stone under short wave light.





And this is the same stone fluorescing pink under long wave light.



You've heard that before, haven't you?  Well, unfortunately, that $5 UV LED flashlight you bought at the hardware store probably isn’t going to work very well with many minerals.  As I mentioned earlier, the inexpensive LED black light lamps almost always emit long wave UV light, but they don't block visible light the way higher-grade ones do. They're mostly good for checking hand stamps for people trying to get back into the bar.   


Since the fluorescence colors are so eye-catching, I can't resist adding some more images to this post.

Below is a fluorescent Willemite and Calcite  specimen from the Sterling Hill Mine in Ogdensburg, in the Franklin District, New Jersey. The Willemite fluoresces green, and the Calcite red.
Specimen under UV Illumination:
Fluorescent Willemite - Franklin
Specimen under standard Illumination:
Willemite - Franklin

Collection and photos: Hershel Friedman


 The colors that fluoresce under ultra violet lights rival the passionate colors of gems. I hope you enjoyed this post and will share it with friends.

Until next time, I'm your Lapidary Whisperer,


No comments:

Post a Comment