Septarian nodule specimens are found in Utah approximately 20 to 40 feet below the surface. Septarians were formed 50 to 70 million years ago when The Gulf of Mexico extended up to what is now the Central United States. So decomposing shell and sea life on the ocean floor had a chemical attraction for the sediment around them, forming concretions (a compact mass of matter). As the oceans receded, the rolling action of the waves resulted in the formation of nodules, that were eventually buried in the mud. As the balls dried and cracked , mineralized solutions, carried by ground water, were deposited into the cracks forming aragonite and golden yellow calcite. The gray mineral is fossilized mud or limestone. I'll post an image later showing what it looks like not exposed to UV light.
I haven't photographed fluorescent minerals before. This was shot with two longwave UV lights (wavelength of 320 nm) and my old Panasonic GH3. I thought it turned out well considering my lack of experience shooting in UV. I thought the patterns were very interesting. The illumination on the right was intentional (or lack of).
A larger version is here;
https://squattingdog.smugmug.com/My-Fir ... -R9KGxdn/A
-JW:
Very interesting and very nice.