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

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. During this process, it also becomes opaque and develops a pitchy luster. Minerals that have gone through this breakdown process are known as metamict. This process is very slow, and one need not worry about a crystallized radioactive mineral breaking down in his lifetime.

Radioactive minerals can be identified with special instruments that detect radiation. The most popular of these devices 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 regular collectors may also acquire inexpensive Geiger counters.

Radioactive minerals are often very similar in appearance, and it may be difficult to distinguish them without x-ray analysis. There are, generally speaking, two appearances of radioactive minerals:

• Those that are bright neon yellow or green
• Those with the typical metamict appearance: opaque and dull with a pitchy luster and rounded crystal edges (or amorphous)

Radioactive minerals emit various forms of radiation, including harmful gamma rays. Many collectors avoid radioactive minerals because of their hazards, but if proper safeguards and precautions are followed, the dangers are minimized and even amateur collectors can collect without worry.

Some guidelines for radioactive minerals:

• Do not collect specimens larger than 2 inches (about 4 cm), unless they will be properly shielded with special lead shielding
• Handle specimens as little as possible; if they are touched wash hands with soap
• Never store specimens, even the smallest of size, in an inhabited room
• Keep all specimens out of children’s reach
• Never eat, drink, smoke, or sleep near a radioactive mineral
• Label all radioactive specimens as radioactive

Some mineral collectors specialize in radioactive minerals. They are very careful and take all necessary precautions. It is best not to collect radioactive minerals unless one is fully knowledgeable about these facts and obeys them.

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