We have seen gemstones seem to glow, and we have witnessed gemstones glowing. This phenomenon occurs when electrons in certain atoms of a crystalline mineral absorb energy and then release it in small amounts over time.
Fluorescent minerals under ultraviolet light – gemstones emit light
Some minerals glow or fluoresce under ultraviolet (UV) light, such as some shown here. Apatite, quartz, orthoclase and muscovite under normal white and ultraviolet light.
Gemstone luminescence can help gemologists distinguish certain natural gemstones from synthetic gemstones. However, to identify gemstones, gemologists often combine other tests to analyze luminescence. Collectors also treasure crystal specimens with spectacular glowing displays.
Collectors rave about the Tagtupu stone found in Greenland because of its intense gemstone glow under ultraviolet light.
What is the difference between fluorescence and phosphorescence?
If the absorbed energy is released almost immediately, this effect is called fluorescence. If there is a delay in energy release (ranging from seconds to hours), this effect is called phosphorescence.
Phosphorescent diamonds - gemstones glow
These yellow diamonds fluoresce magenta or green under ultraviolet light. When UV rays are turned off, they emit a soft green phosphorescent light. Phosphorescent diamonds (crystal size approx. 1 to 1.5 mm), Democratic Republic of the Congo.
What kind of energy causes glow?
X-rays, visible light, and even heat can provide energy to excite electrons in minerals. However, gemologists most often use ultraviolet (UV) rays to trigger gemstones to glow.
Fluorite crystals, general illumination - gemstones glow
Some gemstones fluoresce even in normal visible or daylight light. When backlit with fluorescent or halogen lamps, the transparent areas of this lavender fluorite crystal emit intense “grape juice” purple fluorescence.
What are longwave and shortwave UV?
There are two types of ultraviolet light, long-wave (LW) and short-wave (SW). LW UV light has a wavelength of 3660 Å (or 366 nm). Fluorescent lamps can produce LW ultraviolet light. SW UV light has a wavelength of 2587 Å (or 258.7 nm). Special quartz tubes can produce SW UV light. Some gem minerals show glow in LW, some in SW, some in both, and some in neither. Gemstones from different sources may also have different luminous properties.
Berylite - Gemstones glow
Andulum, from Brazil will emit fluorescent dark green or yellow-green under short-wave ultraviolet light, but andalusite from Lancaster, MA, like the various chiastolite sometimes referred to here in normal white light, will fluoresce under short-wave ultraviolet light brown.
In many cases, UV light does not excite a mineral unless it contains an element of impurity that acts as an activator. For example, manganese plays such a role in many minerals. Conversely, iron quenches fluorescence in most minerals.
Calcium manganate, ordinary light - gemstone glow