Luminescence
Definition
The emission of light by a mineral that is not caused by high temperatures. It includes fluorescence (under UV light) and phosphorescence (continuing after UV is removed).
Example
Fluorite and some Calcite specimens exhibit beautiful luminescence when exposed to ultraviolet light.
Cold Light
Luminescence is the emission of light by a substance not resulting from heat. It is basically "cold light." In minerals, this usually occurs when energy sources (like UV light, X-rays, or even physical friction) kick electrons into a higher energy state. When the electrons fall back to their normal state, they release the excess energy as visible light.
Types of Luminescence
- Fluorescence: Glows only while the energy source (UV light) is on. (Most common field test).
- Phosphorescence: Continues to glow for seconds or minutes *after* the source is turned off (e.g., some Calcite, Sphalerite).
- Triboluminescence: Glows when scratched, crushed, or rubbed (e.g., Fluorite, Sphalerite, Quartz).
- Thermoluminescence: Glows when heated (e.g., Chlorophane Fluorite).