RAPAPORT... Today’s escalating demand for pink diamonds spurred the industry to supply customers with natural, treated, and synthetic pink diamonds. Researchers at Gemology Headquarters International (GHI) recognized that for the protection and edification of consumers it was imperative that they would be able to identify the origin of pink diamonds accurately and cost effectively.
The GHI research team is renowned for its study and identification of High Pressure High Temperature (HPHT) treatments to enhance color of diamonds and Chemical Vapor Deposition (CVD) and HPHT processes to grow diamonds in a laboratory environment. Researchers are continuously identifying and documenting novel color, clarity, and coated treatments. These laboratory enhancements are also used to transform brown and light yellow diamonds into pink ones. Various different processes including radiation, annealing, HPHT treatment and coating are used and often combined to make these modifications.
The research conducted utilized a sample set comprised of 176 pink diamonds ranging in size from 0.01 to 4.02 carats with varying color saturation. The sample also included both loose and mounted jewelry. Origins of the 98 natural pink diamonds include Australia, Africa, and South America. The remaining stones consisted of 38 commercially treated pink diamonds (irradiated and annealed, treated with multi-step processes, and coated with a new deposition method) and 47 laboratory-grown (irradiated and annealed) pink diamonds.
GHI consolidated the power of the existing analytical tests using them as building blocks to develop a new Cross-Reference Identification System (CIS.) To accurately and quickly identify pink diamond characteristics CIS utilizes UV (Ultra Violet) fluorescence intensity and fluorescence spectroscopy measurements. The pink diamonds were also subjected to electrical conductivity testing at different temperatures. Parallel testing was done with established methods on advanced instrumentation (FTIR, UV-VIS-NIR, CL, PL) to verify the results with these two new testing methods. It is well known that the established techniques used individually are neither fast nor conclusive and are challenging in smaller mounted stones. However, a complex combination of data analyses using advanced equipment allowed GHI researchers to perfect the CIS technique.
One interesting finding in the electro conductivity results showed that while all the diamonds had low conductivity, natural pink diamond proved consistently higher than treated and synthetic diamonds with a characteristic difference noted between the pavilion and crown facets.
Branko Deljanin, senior researcher at GHI, commented: “We are pleased with the initial results of the CIS fluorescence testing method, which was developed by Dusan Simic, manager of GHI India. Our next phase has already begun in continuing collaboration with Dr. Alexander Zaitsev, from the College of Staten Island, University of New York, on developing a CIS electrical conductance method that could separate laboratory-grown from treated and natural diamonds of any size.”
A complete presentation of this research will be delivered this month at the European Diamond Conference in Berlin, Germany, September 9-14, 2007.