It’s me again! I got a shortwave UV light for Christmas, and I finally got to check my rock collection for fluorescence! Some rocks I knew ahead of time would be fluorescent, some rocks completely surprised me, and some looked cooler than I ever possibly could imagine. I wanted to show them off, but man, photography’s hard in the dark! But after much playing around with long exposures (and getting a lot of very blurry photographs), I can finally say this: who wants to see my fluorescent rocks?!
Let’s start with some banded fluorite!
Fluorite’s the OG fluorescent rock. It’s so famous for its fluorescence that that’s why the phenomenon is called fluorescence, from the words fluorspar (another name for fluorite) and -essence (state of being). So fluorescence just means: “being like fluorite!” Right away I knew some of my fluorite was going to fluoresce! The zoning (different layers of colors) in this banded fluorite is doing some surprising things, though.
Look at that! Only a few bands of color are fluorescing: those thin blue-green stripes at the top, and the dark, honey yellow at the bottom. Surprisingly, the place that’s fluorescing brightest is that stripe that looks like a very dull, dark brown under natural light. But look at the bright yellow-white it becomes! Under shortwave UV light, I can even see extra zoning bands that weren’t visible to the naked eye!
Let’s test the rest of my fluorite! You might remember my incredibly cool chunk of fluorite from Rogerley Mine. The fluorite of this mine is famous for its daylight fluorescence, meaning it reacts so strongly to UV light that it’ll change color even in regular sunlight! Here’s what that looks like, by the way.
In sunlight, this piece turns a dark blue. But look what it does under an intense UV light! All the translucent crystals turn suddenly opaque, and the entire rock glows a vivid, saturated purple-blue! This is what I think of when I think fluorescence!
These itty bitty pink crystals are spinel! Naturally occurring spinel fluoresces under longwave UV light, but these little crystals were grown in a lab. Lab grown spinel reacts brightly to shortwave UV light, like the one I’m using. It’s one of the easiest ways to tell them apart. These lab grown spinel glow an amazingly bright hot pink!
Here are some of the pebbles from my Big Bowl of Gravel. Shining my UV light around in there revealed a ton of sodalite, a rock which is blue and white under natural light. But with my UV light shining on them, they fluoresce pink and orange! Sodalite is another mineral famous for its fluorescence, so I suspected I’d find these little guys glowing.
A rock often confused with sodalite is lapis lazuli, but you can easily tell the difference by looking for little flecks of pyrite. Lapis lazuli has them, and sodalite doesn’t! But these two rocks even fluoresce similarly. My piece of lapis lazuli glows with stripes of neon orange, but lapis can glow white or pink too.
Here’s a rock I didn’t expect to glow! Fordite is a manmade gemstone, made from the buildup of layers upon layers of paint on car production lines. It’s a way of recycling human garbage and industrial waste into something beautiful, and it’s one of my favorite manmade rocks. But this piece must contain some layers of fluorescent paint, because check this out!
Just like in my banded fluorite, there are layers of paint here that weren’t visible to the naked eye. Some (but not all) of the black paint is turning a turquoise green, and the yellow is suddenly full of bright strips of light yellow and dark orange. Some of the white glows, too! I probably should have expected this, since manmade paints and plastics fluoresce all the time. Some of my figurines and funko pops have fluorescent paint on them too!
Oh man, this one is amazing! This is septarian, a type of fossilized mud or clay. Growing in the cracks in the mud are dark crystals of aragonite and yellowish crystals of calcite. The dark lines of aragonite in this piece are fluorescing a dull orange, and some of the calcite is glowing a pale greenish yellow, fading to blue at the edges. But did you notice the super cool thing happening here?
Even though it all appears the same color under normal light, some of that calcite isn’t fluorescing. You know what? I think that innermost layer isn’t calcite at all, but barite! Barite in septarian nodules is usually pretty white or clear, but this big barite layer was similar enough to the yellow of the calcite that I didn’t even notice it until I saw it under UV light. Welcome to the family, barite! It’s so cool to find new secrets hiding in my old rocks!
Actually, fossils in general are pretty likely to fluoresce. Here’s my petoskey stone, which fluoresces a pale whitish yellow. The color is so subtle in person that I passed over this stone several times before realizing it was fluorescing, but it’s super obvious once you compare the pictures! I wonder what caused that pattern of non-fluorescent spots? Was it the way the rock formed, or did some of the fluorescent minerals get removed when the rock was polished? Either way, what a neat effect!
And as usual, I’ve saved the best for last…
This is amber.
And this is also amber! The bright blue rock with the best fluorescence of all!
This dark, red-orange rock turns super amazingly bright robin’s egg blue under UV light!! (It can be yellow-green, too.) The reaction is so bright and vivid in almost all specimens of amber that it’s one of the best ways to tell it apart from imposter gemstones like copal or manmade resin. There are even some types of amber that exhibit daylight fluorescence, just like my Rogerley Mine fluorite. Look at those swirls and patterns of light and dark blues! The way it highlights the bubbles trapped inside! How the rock goes from dark and translucent to bright and opaque! Amber is absolutely beautiful.
Those are all my fluorescent rocks! I’ve only tested them with a shortwave UV flashlight, so even more of my rocks may fluoresce with a longwave light or simply a more powerful light with better filters! Some of my other rocks surprised me with cool features like tiny, impossible to photograph flecks of fluorescent inclusions. From now on, I’ll be on the lookout for even more amazing, glow-in-the-dark fluorescent rocks!
(You can see more of my rocks over here!)
