What is Luminescence?

Luminescence is the phenomenon in which a material emits visible light when subjected to an energy input. There are different types of luminescence. Some are described below:-

Triboluminescence
Light emitted when a material is struck or broken. Can be seen, in the dark, when some Feldspars are struck with a geological hammer.

Thermoluminescence
Light emitted when a material is heated. Common examples are metals heated to 'red-heat' and light emitted by molten glass.

Fluorescence
Light emitted when a material is subjected to ultraviolet (UV) radiation. This is the luminescence of most interest to mineral collectors as many mineral specimens fluoresce and the colours cover the full spectrum of visible light, from rich red through brilliant yellows and greens to blue and violet.