ADAMAS GEMOLOGICAL LABORATORY publishes gemologically oriented software for the jewelry appraiser, jeweler, or student in gemology or mineralogy. The laboratory also provides technical consulting and jewelry appraisal services to the trade and the public and expert witness services to the legal profession.

BLUE-GRAY  DIAMOND SPECTRA

SAS2000: Developed, Produced And Supported In The USA   Questions, Comments, Product Support
Adamas Gemological Laboratory is proud to introduce to the industry the custom built SAS2000Spectrophotometer Analysis System for diamond and gemstone evaluation and grading. The SAS2000 provides the most accurate colorimetry available today for diamond color grading, helps determine radiation treatments of diamond, provides better ability than the DeBeer's DiamondSure to detect probable  synthetic diamonds , and replaces the spectroscope for transparent gemstone evaluation.

Unusual Blue-Gray Diamond Data
Natural Diamond, Possibly Irradiated (Naturally?)


 


The following spectra of blue gray melee (0.07ct) which was supposedly of natural origin.  These were purchased by a new SAS2000  user, Thomas Hainschwang. The diamonds are NOT electrically conductive (using the Moissketeer 2000SD detector) .(Nitrogen quenches conductivity?). The diamonds exhibit moderate to strong slightly greenish yellow long and short wave fluorescence, long wave stronger than short wave. Phosphorescence, if any, was difficult to guage due to the small size of the samples (0.07 and 0.02ct).  These diamonds had what, when viewed from the crown, at first looked like "right angle inclusions", but appear to be actually multiple laser drill holes, unusual on a 7 pointer.  I have been sent confirmation that other available samples (again about 7 pointers) have similar apparent drill holes.

Blue-Gray Drillhole Inclusions

For a whole series of beautifull photos on these gray-blues stones take a peek at Thomas Hainschwang's GEMLAB site.

Liquid nitrogen cooled spectra did not reveal any hidden absorbance centers in the Vis-Near IR region.

            Typical Blue-Gray Sample Visible Near IR Spectra










Strangely, the 532nm excited Photoluminescence spectra shown below revealed the same characteristic "694nm doublet" seen in 70% of the near colorless synthetic diamond samples we have seen.  The doublet was only seen at cryogenic temperatures.

Room Temperature and LNIS Photoluminescence Spectra

The liquid nitrogen cooled spectra exhibit the  694 Doublet  , which has been only associated with near colorless synthetic diamond to this point.

"694" Doublet

FTIR Data

We obtained an FTIR spectra on January 8th, 2001 courtesy of the European Gemological Laboratory, New York which showed some interesting peaks which strongly suggested ( at the time, based on my misinterpretation of the IR spectra)  that the diamond was possibly synthetic, possibly CVD, (This interpretation of mine turned out to be wrong!)  has high hydrogen content with aggregated nitrogen, and appears to have been neutron irradiated (also incorrect, see below).    Any comment on my interpretation is welcomed. We learn more every day.

My major source for the interpretation of the infra red spectra was Alexander Zaitsev chapter on optical centers in diamond in "Handbook of Industrial Diamond and Diamond Films" ISBN-0-8247-9994-1.

1) Hydrogen Related Peaks at: 3235, 3107, 2920 (2923), 2786,1405cm-1  ( No problem here with interpretation )

2)Possible CVD Related Peaks ( also can be caused by Fingerprints/grease according to Dr. Fritsch- thanks for info) at: 2923, 2854cm-1

3) Synthetic band, enhanced by irradiation, centered at: 2550, with peaks at 1570, 1502cm-1 {Zaitsev states that the 1502cm-1  peak is "observed only in type Ib diamonds after irradiation and subsequant annealing at 750C} However we do not see any radiation induced damage in the visible or Near Infra Red part of the spectrum.

4) Irradiation by Neutrons at 1010cm-1 (However, it is also a subsidiary peak of the B aggregate [ 1175cm-1], which I had missed)

It is interesting to note that in Zaitsev's compilation, published in 1998, he indicates that the  most widely used model of the B aggregate is four nitrogens surrounding a vacancy.  Recently, in other technical literature, including Gems & Gemology, the thinking now is that the B aggregate is composed of  four nitrogens with two vacancies. The B aggregates are "naturally occuring defects in type Ia natural diamonds" {??? are there type Ia synthetics}. It is noted that "A aggregates can be converted into the B aggregates without radiation damage by heating to about 2600C ".

5) Platelets (B2 aggregates)  1370, 1430, 780cm-1 ( these are not seen in CVD per Prof. Alan Collins)

6) Irradiated, Possibly H1a center at 880, 1450cm-1 (however this pair [actual three peaks which include 1095cm-1 which is in the region of saturated data shown and not dicernable] is also seen in type Ia diamonds, with a possible "origin being inclusions of carbonates".

Summary Conclusion To Date
Natural Diamond, Possibly Irradiated





Here is the full size gif on the infra red spectrum..

 
 

 SAS2000 Spectrophotometer   Questions, Comments, Product Support AD