Fluorescent Minerals: Glowing Geology

Fluorescence is one form of ‘cold’ emission of light (luminescence), rather than from the heated state of incandescence. Fluorescence occurs through the excitation of atoms, molecules, or physical structure (lattices) through the addition of energy in the form of electromagnetic radiation (here, that would be ultraviolet light). The fluorescent emission is a lower energy state (a longer wavelength) than the absorbed light. Fluorescent rocks usually have activators, or trace minerals, that interact with their own atoms, allowing fluorescence to occur. Willemite, for example, uses manganese as an activator. A few minerals are self-activating, and do not require the addition of other elements.

Fluorescent rocks can be found all over the world. In order to look for them, you will need an ultraviolet light. UV lights used to be bulky and expensive, but now you can acquire LED flashlights with appropriate filters in shortwave, midwave, and longwave emission from rockhound dealers. Visit some online fluorescent rock forums for brand reviews. Most of the rocks I am photographing here are shown under shortwave light. (The sodalite is shown under longwave light.) A few rocks are known to glow different colors under longwave and shortwave lights. There are many fluorescent rock dealers online, but if you are just starting a collection, I would recommend sticking to inexpensive material.

Be aware that you should never shine a UV light into eyes, and limit exposure to skin. (Basically, just point the flashlight at the rocks; make sure kids are carefully supervised.)

A mineral's ability to fluoresce varies from location to location, as it depends greatly on mineral composition. Too much of an activator may quench fluorescence, while the presence of other trace elements may alter coloration. Fluorite in one location may glow blue, in another location it may glow cream (or yellow, white, green, red, etc.), or it may not glow at all. (And, of course, fluorite under natural light may be found in a wide range of colors, making it a prized focus of many collections.)

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fluorescent minerals

Glowing Geology

Calcite

What is Fluorescence?

Chalcedony (?)

Where can you find fluorescent rocks?

Yellow Calcite

Elk Creek, South Dakota

Differences

Fluorite and Celestite

Clay Center, Ohio

Further reading

Tabular Calcite

Chihuahua, Mexico

Chalcedony

Safford, Arizona

Botryoidal Fluorite

Cañon City, Fremont Co., Colorado

Fluorite on Amethyst

Unaweep Canyon, Colorado

2021-2025

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