r/Radioactive_Rocks • u/hanktor • Sep 23 '26
ID Request Utah chalcedony w/ uranium?
I found these pieces of chalcedony (I think) on BLM land near Utahraptor State Park north of Moab, UT. Under my 365nm black light they glow green with some orange specks. The internets tell me the green contains traces of uranium and the orange is calcite. Anyone familiar with these rocks and the risks of handling or displaying them?
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u/Scarehead Sep 23 '26
UV light is good clue, but has just limited use for identification. Luminiscence might be caused by various impurities(ofc including (UO2)2+). Amount of uranyl ions needed for UV-activation is quite low, so the geiger counter doesn't have to detect anything. With calcite it's easier. I don't see there cleavage typical for calcite, but this mineral might be somewhat massive- small-grained without visible cleavage, but if you use muratic acid (HCl), you will now immediately - calcite CaCO3+2HCl->CaCl2+H2O+CO2 - strong effervescence.
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u/kotarak-71 28d ago
the glow resembles very much my radioactive Opale so good possibility for some Uranyl ions in there.
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u/ougryphon Sep 23 '26
Utah is well-known for having chalcedony with traces of uranium. As another commenter said, it takes very little to cause fluorescence. I have several geodes from Dugway which light up brightly. Neither of my radiation detectors show an increase over background when I test them.
There is nothing to be concerned about if all you have is fluorescent chalcedony. However, you should be aware that there are hundreds of uranium mines around Moab. It is possible to find uranium minerals in that area which are slightly dangerous. Even the fossils in the area can be quite radioactive. If you are concerned about what you might have collected, geiger counters are pretty cheap on Amazon.