Fluorescence in minerals occurs when a specific wavelength of light such as ultraviolet (UV) light, electron beams or x-rays are directed at it. This light excites electrons in the mineral causing them to temporarily jump to a higher orbit in the atomic structure. Once the electron returns to its previous orbit, a small amount of energy is released in the form of a different wavelength of light than what's being shone onto it. This produces a visible colour change of the mineral that we see and is the phenomenon known as fluorescence.
Only about 10% of minerals have a fluorescence that is visible to humans, these minerals must contain 'activators' (cations of metal) in specific concentrations. Different metal activators will produce different colours.
Willemite, franklinite and calcite under normal light. This specimen hails from Sterling Hill near Franklin, New Jersey, U.S.A. Dubbed the 'Fluorescent Mineral Capital of the World' Franklin is home to approximately 60 different fluorescing minerals.
The next slide shows Willemite (green), franklinite and calcite (red-orange) under UV light. Only the franklinite does not fluoresce.
Pictured are some of the UV lamp equipment used during the photography work. The large lamp has a selectable split-tube 254nm shortwave and 365nm long wave light source as some minerals fluoresce at different wavelengths. Whilst the UV pen was used to focus the light onto specific areas of particular minerals, such as the apophyllite specimen shown earlier.
The National Mineral and Commonwealth Paleontological Collection, Geoscience Australia and The National Museum of Australia Mineral Collections (specimens).
Some specimens loaned from the Peter Butler Collection.
Chris Fitzgerald (photography).
Steven Petkovski (text).
Dave Champion (scientific review).
Copyright for content: http://www.ga.gov.au/copyright