By Francesco Natale (Chief Gemologist - IDL Dubai)
Few days ago we received a jewelry set from a client. It was composed of a necklace, a ring and one pair of earrings. It was 18k white gold containing "colorless" diamonds and "Fancy intense" yellow to orangy-yellow diamonds.
The "white" stones where identified as natural diamonds with natural color.
The fancy color ones raised some questions as soon as we started the visual observation of the color and internal characteristics.
What was immediately suspicious was the absolute uniformity of the color of all the stones (approx 90), showing identical tones and saturations.
After microscopic observations it was clear that further research was needed to clear the origin of the stones.
In such cases advanced testing is required to prove the origin, natural or synthetic, of the stone and the origin of the color, natural or treated.
We asked the owner of the jewels to unmount few yellow diamonds to be able to perform all the necessary measurements and analysis that would be impossible to do in mounted conditions.
What was visible with magnification were some suspicious internal characteristics such as:
It was becoming clear that the next step of the research had to focus on the "natural vs synthetic" determination of these stones.
The FTIR (Infrared spectroscopy) confirmed that all the samples were type Ib diamonds. It means that they contain single N (nitrogen) atoms as impurity in the structure of the diamond, providing the typical yellow color of these stones.
This is important information since all the synthetic yellow diamonds, created with the "HPHT" method, are type Ib.
A further analysis on the UV-Vis-NIR spectrometer showed again typical spectra for this type of diamonds.
Only one of the stones had relevant peaks referable to the presence of the metallic element "nickel" inside the stone. The laboratory process to create synthetic diamonds involves the use of some "solvents" containing metallic elements such as "nickel".
Natural diamonds don't contain this element so this was again an important information regarding the origin of these stones. Probably the most decisive instrument that can prove the natural-synthetic origin of a diamond is the Diamond View (from DTC).
It's an instrument working on the basis of the "fluorescence pattern" of the stone when exposed to very low wavelength UV light.The way the crystal grows, deep inside the earth or in a laboratory, results in different arrangement of the internal structure. This is visible, even in faceted stones, as different patterns of the growth sectors reacting (or not) with different colors to the UV radiation.
In our specimens we observed clear evidence of a "cubo-octahedral" structure of the crystal that is typical of synthetic diamonds.
So after a series of standard gemological observations and advanced research analysis we were able to confirm the Synthetic origin of the diamonds we received from the client.
We only tested 4 stones (taken as representative samples) out of approx 90 mounted in the jewelry set but we can confidently consider that all of them are of the same synthetic origin.