Didn't realize it until after I'd actually posted the wrong file. Sorry about this. They disintegrate at a steady rate whether they are pure elements or part of a mineral's composition. The three types of radiation that are given off are alpha, beta, and gamma particles. Alpha particles only travel a few inches and are stopped by a few sheets of paper.
Beta particles travel up to a foot and are stopped by a thin sheet of metal.
Gamma rays travel several hundred feet in the air, penetrate almost one meter of water, or one foot of rock. Excessive exposure to radioactivity can damage living cells. Therefore it is dangerous to wear radioactive minerals close to your body or carry them around in your pocket for any length of time. Even the short-range alpha particles will reach your body if you place the radioactive material against your skin. It is wise to wash your hands after handling radio active minerals.