Despite what Hollywood shows of neat radioactive materials, you'll never run across any stone that just glows all by itself.
There are several ways that minerals can emit light, besides the light that is emitted from exposure to daylight or the light from normal light bulbs. Some of these ways involve special lamps that emit ultraviolet light. The light from these UV lamps reacts with the chemicals of a mineral and causes the mineral to glow; this is called fluorescence. If the mineral continues to glow after the light has been removed, this is called phosphorescence. Some minerals will glow when heated; this is called thermoluminescence. Finally, there are some minerals that will glow when they are stuck or crushed; this is called triboluminescence (and really cool to see).
The fluorescent minerals are minerals that emit visible light when activated by invisible ultraviolet light (UV), X-rays and/or electron beams. Certain electrons in the mineral absorb the energy from these sources and jump to a higher energy state. The fluorescent light is emitted when those electrons jump down to a lower energy state and emit a light of their own. Among hobbyists, walking around with a UV lamp at night is an entertaining way to look for minerals.
There are two kinds of ultraviolet light, longwave and shortwave. Longwave UV light is known as "black light" and most people are familiar with its effects of making white clothing glow in the dark. This is due to whitening chemicals in detergents.
Shortwave UV light is by definition of a shorter wavelength than the longwave UV light. Shortwave lamps which are available to collectors, can be very entertaining and useful to identify minerals, however it is dangerous to look at the shortwave light source, as doing so can cause blindness - just have to say that in case you're interested.
You may see a cool watch that appears to glow on its own. But you can't, because light is energy, and you can't get energy from nothing (a basic Law of Physics). In these watches (and so on), phosphor, a chemical substance that radiates visible light after being energized (just like emergency glow lights) is mixed with a radioactive element, and the radioactive emissions energize the phosphor continuously. In the past, the radioactive element was radium, which has a half-life of 1,600 years. Today, most glowing watches use a radioactive isotope of hydrogen called tritium (which has a half-life of 12 years). Some use promethium, a man-made radioactive element with a half-life of around three years.
However, even in this water
· 1 decade ago