HOT ROCKS

A Rockhound’s Guide to Radioactivity

- STEVE VOYNICK

During the late 1940s and early 1950s, Colorado, Utah, and New Mexico hosted what was called the “Great Uranium Rush” (Rock & Gem, April 2017), the last mineral rush in which individual prospectors had a chance to strike it rich. The quest was for, in the parlance of that era, “hot rocks”— rocks emitting elevated levels of radioactivity that might indicate a uranium deposit worth millions of dollars.

A few prospectors did indeed make their fortunes. Still, most received their reward by participating in an adventure that thrilled the nation and introduced words and terms like “radioactivity,” “Geiger counter,” and “radiometric prospecting” into the general vocabulary.

Although finding a million-dollar uranium deposit today is unlikely, understanding radioactivity and knowing how to detect it can greatly enhance the mineral-collecting experience. Radioactivity is one of the fascinating physical properties of minerals. It is ionizing energy in the form of particles and rays produced by the spontaneous disintegration or “decay” of unstable atomic nuclei.

While this definition might seem a bit intimidating, getting a practical handle on radioactivity is not that difficult. Admittedly, the word is loaded with negative connotations linked to nuclear weapons, fallout, toxicwaste disposal, reactor meltdowns, and the hazards of radon gas. Nevertheless, radioactivity is very much a part of the natural world, especially the world of mineralogy.