One of my childhood hobbies was to go out to the desert with my dad to explore abandoned mines and collect fluorescent minerals at night (fossicking is the Australian term for collecting minerals). Once the sun had set, which happens pretty early in the winter, we’d head out onto the mine tailings with a portable Ultraviolet lamp to look for rocks that glow a variety of candy like colors under the powerful UV rays. Now, about ten years later, I’ve revisited my old hobby and started to photograph the marvelous phenomenon. Standing out on a calm desert night under the expanse of stars is magical enough, but seeing the technicolor rocks come to life under the ultraviolet light takes it to another level. I suppose some might say it’s reminiscent of the fantastical world of Pandora in the recent blockbuster hit ‘Avatar’, but in this case, it’s actually real!

Scheelite (the white specks) seen under daylight (left) and the visible fluorescence caused by Shortwave Ultraviolet radiation (right).

Very briefly, fluorescence is a natural phenomenon in which electrons in the atoms of certain minerals will absorb the high energy ultraviolet light, and subsequently release that energy at a different wavelength in the visible spectrum. The visible light is referred to as fluorescence, and can come in a variety of wavelengths – ie. colors – including red, green, blue, white, etc. For a more in depth description I refer you to the definitions provided by the Fluorescent Mineral Society here:

Incandescence is light from heat energy. If you heat something to a high enough temperature, it will begin to glow. When an electric stove’s heater or metal in a flame begin to glow “red hot”, that is incandescence. When the tungsten filament of an ordinary incandescent light bulb is heated still hotter, it glows brightly “white hot” by the same means. The sun and stars glow by incandescence.

Luminescence is “cold light” that can be emitted at normal and lower temperatures. In luminescence, some energy source kicks an electron of an atom out of its lowest energy “ground” state into a higher energy “excited” state; then the electron returns the energy in the form of light so it can fall back to its “ground” state. With few exceptions, the excitation energy is always greater than the energy (wavelength, color) of the emitted light.

Fluorescence and Photoluminescence are luminescence where the energy is supplied by electromagnetic radiation (rays such as light, which will be discussed later). Photoluminescence is generally taken to mean “luminesce from any electromagnetic radiation”, while fluorescence is often used only for luminescence caused by ultraviolet, although it may also be used for other photoluminescences. Fluorescence is seen in fluorescent lights, amusement park and movie special effects, the redness of rubies in sunlight, “day-glo” or “neon” colors, and in emission nebulae seen with telescopes in the night sky. Bleaches enhance their whitening power with a white fluorescent material.

Fluorescent minerals can be found anywhere, but the highest concentrations and most interesting specimens are often found on the tailings of old mines (or deep inside the mines, if you dare go there). Not just any mines, of course – certain ores tend to be associated with minerals that fluoresce while others won’t have any at all. Finding those mines is part of the adventure. By day you can rarely tell if a rock will glow under the UV lamp, so you’ve got to go exploring at night, being mindful of the vertical mine shafts, old rusted mining equipment, scorpions (which, I can say from experience, glow bright green), and other dangers. Two weeks ago I visited two Tungsten mines, one near Bishop, and another near Darwin (on my twilight/lightpainting workshop). One of the primary ores for Tungsten is Scheelite, a very dense mineral that glows white/blue under shortwave UV light. Other common minerals shown in these images include Calcite (glows red), Silica coatings containing Uranyl ions (glows green), and ‘desert varnish’ (glows yellow/white).

Tungsten Hills

“Tungsten Hills” ~ Tungsten Hills, Bishop, CA
The Tech: Canon 5D2, 16-35mm mkII, tripod, Shortwave UV lamp
Exposure (rocks): iso 1600, f/10, 8 min
Exposure (stars): iso 3200, f/2.8, 30 sec
Processing: Complex exposure blending

Given the restrictions on where these rocks can actually be found, compositions are typically rather limited – by my usual standards this one from Bishop isn’t quite as dynamic as I like, but it shows the phenomenon in a unique mountain view setting. Also, I was lucky to witness another special phenomenon seen only on very dark and clear nights far from any light pollution: the Zodiacal Light. This light, which may at first appear to be light pollution (which is usually round, rather than a columnar/triangular beam, and orange/red rather than white), is actually sunlight reflected off the cosmic dust found in our Solar System. At midlatitudes it’s best seen in the western sky after evening twilight in springtime, or before the predawn twilight in the fall.

“Moonlight Fossicking” ~ Darwin, CA
Click to view this on my website to see better details.
The Tech: Canon 5D2, 16-35mm mkII, tripod, Shortwave UV lamp, LED headlamp
Exposure(s)/Processing: ten exposures, complex processing (but honest to reality, save for the UV purple beam which was added in photoshop for added context). Consider taking a night photography workshop in the future to learn how to take images like this!

This second image was taken at a Tungsten mine near Darwin, CA. Here I wanted to depict several aspects of the experience of collecting fluorescent minerals: the essence of the night including the stars and moon, the diverse and otherworldly collection of fluorescent minerals out there, the history of the mining era that exposed these rocks, and of course the human element to give some context to the strange glowing rocks and help to tell the story. I was able to bring all these elements together through the creative use of “light painting” (both with my headlamp as well as the UV lamp), and blending 10 individual exposures (without moving the camera) over the course of about two hours of work. The excessive number of exposures was only necessary to overcome the limitations of the technology by using various iso, aperture, and focus settings to bring everything into focus, illuminated, and with as high an image quality as possible. One day such images may be possible in a single exposure, I can’t wait!

Darwin, by the way, must be a contender for the strangest towns in California. Imagine a ghost town, similar to Bodie, but one where 40 people actually still call it home. The number of rusted and broken down cars exceeds the human population by close to a factor of 3. Amazingly, there is a dance hall and post office on main street, but it’s unlikely anyone has danced in the dusty shack since wild west gun fights broke out over the poor wages of the silver-lead mining of the 1870’s. While the town peaked in population and productivity around 1876, at which time it was actually a booming establishment, active mining did continue up through the 1970’s. One can only wonder who lives there now. At least they get to enjoy some peace and quiet being about an hour drive from the nearest reasonably sized town (Lone Pine). I hope to revisit some other mines over the course of the next year, so stay tuned for more fluorescent adventures.

* * * New Material * * *

Since writing this post I returned to photograph the Darwin mines again to come up with this image. You can read the associated blog post here: Fluorescence.

click image for details

Fluorescent minerals

A variety of fluorescent minerals under shortwave and daylight illumination. Included are several specimens from Franklin NJ, Fluorite, Scheelite, Halite, Zircon, and Uranium ore.

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8 Comments to “Moonlight Fossicking”

  1. Derrick says:

    Floris – what an awesome post. Thanks so much for making it. I can’t wait to take my son out to try this now! You made beautiful images to accompany the post too.

  2. Aleks says:

    There is a quary in Franklin, New Jersey where a lot of fun, glowing rocks are found. I believe one of them is called Franklinite after the town. I still have boxes of these at my parents house in NJ.

  3. Hey Aleks – yep, I have some nice pieces of ‘Franklinite’ at home, I would absolutely LOVE to get out there to try some of this. Not sure what the access is like though.

  4. Kari Post says:

    This is soooo cool. Geology rocks!

  5. […] it earlier this year, so if you’re curious to know exactly is going on here please read: Fluorescent Minerals. This time I came with the intent of fine tuning my composition, as well as making sure to get the […]

  6. Chris says:


    Way to mix science and photography all in one. As I budding Geologist I have really enjoyed this post, and your more recent one. I will definitely be out trying this out with my kids!


  7. […] is the emission of light by living organisms through chemical reactions (very different from fluorescence and phosphorescence). There are a number of biological organisms capable of bioluminescence, […]

  8. […] is the emission of light by living organisms through chemical reactions (very different from fluorescence and phosphorescence). There are a number of biological organisms capable of bioluminescence, […]