Radioactivity in minerals are caused by the inclusion of naturally-occurring radioactive elements in the mineral’s composition. The degree of radioactivity is dependent on the concentration and isotope present in the mineral. For the most part, minerals that contain potassium (K), uranium (U), and thorium (Th) are radioactive.

Radioactivity is an attribute of minerals that contain radioactive elements. Radioactive elements are elements that contain disintegrating nuclei, emitting alpha rays, beta rays, and gamma rays. Uranium and thorium are the best known radioactive elements. Minerals that contain these elements in their chemical structure will be radioactive.

Radioactive minerals are unstable, meaning the elements in their structure continually break down. This destroys the mineral’s crystal lattice, causing it lose its crystal shape. When this happens, its crystal edges become rounded, and the mineral eventually becomes amorphous.

Radioactive minerals can be identified with special instruments that detect radiation. The device used to measure this is the Geiger counter. Electric charges develop in a Geiger counter when it is placed near radioactive material; this can measure the presence and intensity of radiation. Geiger counters are normally used by scientists and specialists, but collectors may also obtain inexpensive Geiger counters.

Table of Naturally Occurring Radioactive Isotopes