How does a sun-tanning lamp differ from one used to make rocks and minerals fluoresce?
The tubes/lamps/bulbs used for rock collecting usually have a relatively narrow band of UV emission and they do not generally use blends of phosphors as the sun tanning lamps do. The fluorescent response of many minerals can be very specific to the wavelength. For example, some calcite from Mexico fluoresces three different colors depending on the wavelength to which it is exposed. This calcite fluoresces a bright blue-white under UV C radiation with a peak of 254 nm, yellow under some UV B tubes/lamps with a peak around 315 nm, yellow under UV A with a peak of 352 nm, and hot pink under UV A with a peak of 368 nm. If such a specimen of calcite is exposed to a sun-tanning lamp, the fluorescent response would probably be mixed such that the pink and the yellow would blend into a salmon color. A relatively small number of other minerals also exhibit a different response to various UV wavelengths, so mineral collectors prefer UV tubes/lamps with relatively narrow emission bands.
