RESULTS
The results of the spectroscopic measurements are
described below according to three main categories
of diamonds that exhibit similar fluorescence spectra
at long wavelengths. In most cases, these categories
corresponded well to the diamonds’ bodycolors,
which are discussed within each grouping. FTIR
and UV-Vis-NIR spectroscopic data are also
described below. Phosphorescence spectra for these
samples, and for an additional 32 natural-color diamonds
from the Aurora Heart and Aurora Butterfly
collections, can be found in the G&G Data
Depository at www.gia.edu/gemsandgemology. A
summary of the phosphorescence results for the
natural-color diamonds is reported in box B.
Category 1: Fluorescence Spectra with Dominant
Peaks at ~450 and ~490 nm. All diamonds described
in this section showed similar fluorescence spectra
(see, e.g., figure 4). Most of the natural-color diamonds
had yellow, fancy white, and pink bodycolors,
but one green and one gray-green natural-color
diamond also followed this fluorescence pattern. Six
irradiated diamonds also showed this fluorescence
pattern with weak-to-moderate intensity; they had
green to greenish blue bodycolors.
All 10 pink diamonds, including the DeYoung
Pink, showed moderate fluorescence with peak
intensity at ~450 and ~490 nm. One pink diamond
examined with the high-resolution spectrofluorometer
(GIA 21194) showed the zero-phonon line (ZPL)
at 415 nm related to the N3 defect and its lowerenergy
(higher-wavelength) sideband.
In general, most yellow diamonds show weak or
no fluorescence; of those that do fluoresce, blue has
been reported as the dominant color (King et al.,
2005). Here, three of the four natural-color yellow
diamonds without a greenish component exhibited
moderate-to-strong fluorescence with peaks at ~450
and ~490 nm.
The three fancy white diamonds showed moderate
fluorescence peaks at the same wavelengths.
One green and one gray-green (chameleon) diamond
showed moderate-to-strong fluorescence intensities
that were consistent with category 1.
Absorption Spectra. The UV-Vis-NIR spectra for
three natural-color diamonds and three treated samples
from the GIA collections with category 1 fluorescence
showed the N3-related ZPL at 415 nm.
The FTIR spectra of these diamonds, as well as four
diamonds from the Aurora Butterfly collection,