Some specimens that contain a mixture of minerals will respond best to
several wavelengths of ultraviolet. Full-Wave UV requires a SW, MW, and
LW fluorescent light. The specimen above is from the Purple
Passion Mine near Wickenburg, Arizona. It contains calcite (red), willemite
(green), and fluorite (purple). Most fluorescent minerals that respond
to more than one wavelength will exhibit the same color in a different
wavelength, but one of the wavelengths typically has a brighter response.
Three wavelengths are used since there are currently commercial UV fluorescent
light tubes available in only three wavelengths.
Images © 2003 James O. Hamblen