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New HPHT Detection Clue
Jewelry Scene


EGL USA has discovered a visual clue that a diamond has been high pressure-high temperature treated. The “fluorescence cage,” a specific luminous intersecting pattern along the cut edges and vertices of facets, can be seen with a fluorescence microscope. It is visible in colored HPHT-treated Ia diamonds with less than strong fluorescence.

Dr. Inga Dobrinets of EGL USA completed the research identifying the cage, in collaboration with Professor Alexander Zaitsev of the College of Staten Island/CUNY. Early research indicates that the effect results from the movement of optically active impurities, triggered by the HPHT process.

“The visual observation of a fluorescence cage appears to be the most reliable feature used so far for the reporting of HPHT treatment,” says Dr. Dobrinets.

“A significant advantage of the cage-based identification is its comprehensive fidelity and technical simplicity. While the ‘cage effect’ may not appear on all HPHT-treated stones, when it is evident, a conclusive identification can be made on that basis alone.”

“In the coming months, we plan to put this breakthrough to practical use—to provide HPHT identification in a more efficient and cost-effective way,” says Mitch Jakubovic, director of EGL USA.

“We don’t yet know what percentage of HPHT diamonds show this effect, but our findings so far are that 100 percent of HPHT diamonds can be identified this way,” says Rachel Halpert, spokesperson for EGL.





Cage patterns in HPHT treated diamonds.
Cage patterns in HPHT treated diamonds.
Photos: EGL USA.