The Gemological Laboratory has been engaging in
gemological research, colored diamond identification, colored diamond grading, and gemstone identification
services. We issue gemstone identification report with necessary spectral curve,
such as VU-VIS-IR spectrum, UV fluorescence spectrum, photoluminescence
spectrum, FTIR spectrum for jadeite identification. We include a digital image of
the reported gemstone in the report. The digital image can be used as a digital
"fingerprint" and saved for future rechecking.
We use the Liulabs MDIS-i6 multifunction dual integrating
sphere spectrometer to measure the spectra of visible reflectance, UV
fluorescence and photoluminescence, and a FTIR spectrophotometer to measure the
IR spectrum for identifying colored diamonds.
Depending on the color and
the spectral peaks of the colored centers in the visible spectrum, UV
fluorescence spectrum and photoluminescence spectrum, such as the N3, H3, H4,
550 nm, NV, S-V and GR1 centers, the origins of most colored diamonds can be
identified as natural, synthetic, treated or other mixed types. The IR spectra
are also used to identify the types and other characteristics properties of
colored diamonds for identification purposes.
Color Gemstone Identification
We identify colored
gemstones by spectroscopy methods using the Liulabs multifunction spectrometer
and FTIR spectrophotometer. We measure the visible, UV fluorescence,
photoluminescence and IR spectra of gemstones, and compare the spectra with the
spectra in our database to identify each gemstone. Our spectroscopy method for
gemstone identification is much more advanced than the traditional gemological method
using spectrocope, refractometer, microscopy etc.
Color Grading of Colored
Diamonds and Gemstones
We use the Liulabs multifunction spectrometer and the
computer color grading system to grade the colors of colored diamonds and
gemstones by the Universal Color System. We also provide color grades of
the modified color grading system of GIA for colored diamonds (see Figure 1). In addition, our color
grading report includes the CIELAB a*, b*, hue, saturation and lightness, which can be
used for pricing colored diamonds precisely. The visible spectrum, UV
fluorescence spectrum, photoluminescence spectrum, and IR spectrum
measured by the Liulabs spectrometer and FTIR spectrophotometer can be provided
Figure 1. Spectral
measurement and color grading of a treated synthetic fancy vivid greenish blue
diamond by the Liulabs multifunction spectrometer.
and Color Grading
We provide jadeite identification service
using the Liulabs multifunction spectrometer, FTIR spectrophotometer, and an advanced digital imaging system. Our Identification Report
including five sections: Sample Description, Picture, IR Spectrum, Color Grade,
and Conclusion. The weight, size, color, cut of a tested sample will be described in
the Sample Description section. We have developed an advanced digital imaging
system for gem identification. This system can also provide a high resolution
digital image, which is usually used for picture in the Report. We will store
this digital image as "fingerprint" of the sample for future identification
purpose. We assign the types of A B, C, or B+C based on the IR spectrum and
visible spectrum. The color grade is directly provided by the Liulabs
spectrometer with the Jadeite Color Grading plug-in software. In the
Conclusion section, we give a precise conclusion without any confusion.
Figure 2. Jadeite color
grading of the Liulabs multifunction spectrometer.
Grading of the
The alexandrite effect refers to the color change of gemstones under
different light sources. It is a non-color-constancy phenomenon. The gemstones
with the alexandrite effect are usually more valuable and sought after by
collectors. The alexandrite effect has been classified into four categories
depending on the hue change under different pairs of light sources.
The plug-in software
of Alexandrite Effect Grading can grade the alexandrite effect of gemstones
under CIE standard illuminants A, D65, F7, and F11 (see Figure 3). There
are 6 alexandrite effects between different CIE standard illuminants, and 5
grades based on the hue angle differences in the CIELAB color space. The 5
grades of the alexandrite effect are None, Weak, Intense, Strong, and Vivid.
The hue angle change ranges of the 5 alexandrite effect grades are: