Gemstones and Fluorescence – Who Knew!?


I learned something new recently (at least new for me). I accidentally discovered, through an unrelated web search, certain gemstones exhibit fluorescence under ultraviolet (UV) light. Now, this may not be news to some of you, but it surprised me!


What is fluorescence and why do some gemstones exhibit it and others don’t? According to an article by Hobart M. King, PhD, RPG on, certain minerals can absorb a small amount of light and then emit a small amount of light in a different wavelength. This change in wavelength appears as a color change to the human eye. Here is a link to the article so you can see more for yourself!

Additional research taught me fluorite, rubies, some emeralds, and diamonds fluoresce. What do I have from my many rock hounding trips to the North Georgia Mountains? Rubies and emeralds (no diamonds, but I may be headed to Arkansas later this year to see if I can find a diamond or two, but that will be another post)! No fluorite that I know of, though. To test my rocks, I asked for a UV flashlight for Christmas and I was lucky enough to get one.

Checking my rock collection:

After the Christmas festivities were complete (including a delicious prime rib linked here), I spent time examining my rock collection for signs of fluorescent stones. Guess what? I found some! The rubies show up well (chromium, which gives rubies their red color, is an activator for fluorescence) and a few of my better emeralds have a slight reddish glow. Who knew? I wondered why the sapphires didn’t fluoresce and discovered that iron can dampen fluorescence, even though the titanium can acts as an activator. Both of those elements give sapphires their blue color. Here are a few pictures to illustrate the change with the UV light. The first two are rubies under regular light and then under the UV light. I love the pink color!

Rubies without fluorescence
Gemstones Under fluorescence

The next two pictures are of a yellow rock that I really don’t know what it is, but it glowed a lovely pale green under the UV light.

Fluorescence Yellow Rock
Yellow Rock under Fluorescence

I realize using a long wave UV flashlight like I received at Christmas will not show the fluorescence on all the stones that possess the property. For that, I’d need a shortwave UV lamp. I may have to order one to see what the difference between the two devices is. If I can get one that is portable, I can take it with me and use it during my rock hounding excursions.

Safety First:

If you decide to use a UV light, make sure to use it safely. UV light is the same light that causes sunburn, so don’t shine the light on your skin. Don’t look into the light directly and don’t shine it on another person or a pet. Wear UV protective glasses, too!

Did you know about gemstones and fluorescence? Leave me a comment and let me know. I’d love to see some of your pictures. As I find more fluorescent stones, I’ll try to post pictures.



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