CATALYST

Rocks and minerals come in a stunning array of colors — from vibrant purple fluorites to sparkling white marble. But that’s not all — many minerals have secret colors that can only be seen in the dark. That’s right: rocks can glow in the dark!  

This spectacle occurs because some rocks contain minerals that emit a colored light when exposed to ultraviolet (UV) or “black” light. This phenomenon is called fluorescence. Some minerals like pyrite are never fluorescent, while others like autunite are always fluorescent. Most minerals fall somewhere in between and may fluoresce depending on where they formed and what compositional impurities they have. Many of these fascinating fluorescent minerals will be displayed in a special case in the upcoming renovation of the Museum’s classic Gems and Minerals Hall.  

The science behind these fluorescent colors is almost as dazzling as the rocks themselves. Fluorescent minerals can emit green, yellow, blue, red and many other colors of light when exposed to UV light. Just like visible light, ultraviolet light has energy. In fact, it’s this energy that burns our skin when we stay in the sun too long. When high-energy UV light hits a mineral, it energizes electrons within its atoms, causing the electrons to jump to a higher energy state. When the electrons fall back to their original position, the energy is released as visible light. That light meets our eyes, and we see it as a color. The specific color depends on the wavelength of the energy released. 

For the new mineral hall, the Museum plans to create a large display of rocks and minerals that shows a full “fluorescent rainbow” of color. This fluorescent mineral case is just one of over 60 new cases planned and will be one of the largest in the new exhibition. It will showcase hundreds of specimens from around the world, including over 75 mineral species and even a few glow-in-the-dark fossils!  

Assembling the specimens for this case was nothing short of an adventure. We knew we had at least a small number of fluorescent minerals in our collections, but because most specimens were collected for other reasons, we had no idea how many fluorescent minerals there actually were. To search for these hidden treasures, we surveyed the entire geology collection, as well as the current Gems and Minerals Hall with UV flashlights. No small task!  

With help from a bevy of volunteers and fluorescent mineral experts from our regional mineral community, we gathered in the dark after hours  to examine every single rock and mineral in the Museum’s collections — over 20,000 specimens. Over the course of several months, we assessed the brightness, color and UV sensitivity of thousands of fluorescing specimens. Among them, we identified a few stunning “glowers” that we plan to display in the new mineral hall. One of our biggest surprises?  Many of these fluorescent treasures are hidden in plain sight — already on display in Coors Hall of Gems and Minerals.  

Another surprise was discovering that our collection lacked fluorescent minerals from certain parts of the color spectrum, and from several iconic fluorescent mineral sites. Luckily, the local fluorescent mineral community was more than happy to help, donating specimens to fill the gaps. Former Fluorescent Mineral Society President Conrad North offered nearly a hundred specimens from his own collection, representing a smorgasbord of groovy glow-in-the-dark geology. With such generous donations of specimens, time and expertise, we’ve nearly acquired all the specimens for this new fluorescent mineral display.  

Soon, you too will be able to experience the full spectrum of fluorescent minerals — alongside many other geologic wonders — in the forthcoming Dea Family Gems and Minerals Hall.