Numerous natural-color colored diamonds from the Aurora Butterfly of Peace and other collections
were studied using a new type of fluorescence spectrometer that has many advantages for
gemological research, including high portability, low cost, and rapid collection times. For comparison,
10 irradiated diamonds were also studied. With only two exceptions, the natural-color
diamonds could be separated into three categories—based on the peak wavelength and shape of
the fluorescence spectra—that generally corresponded to their bodycolors: (1) ~450 and ~490
nm, recorded mainly for pink, yellow, and fancy white diamonds; (2) ~525 nm, mainly for greenyellow
or yellow-green and brown diamonds; and (3) ~550 nm, mainly for orange, gray-green
(including chameleon), and type Ia blue-gray or gray-blue diamonds. A spectrum that is anomalous
for the diamond’s bodycolor may indicate that it has been treated, and in some cases, fluorescence
spectroscopy can help determine diamond type.