Rapaport Magazine

Investigating A New Treatment

Low Pressure-High Temperature is the latest development in diamond treatments.

By Marc Goldstein
High Pressure-High Temperature (HPHT) treatment to improve the color of diamonds by subjecting them to high pressure and high temperatures has been around since the 1990s. But it has its limitations. It is only effective with type II diamonds, which represent approximately 1 percent of all diamonds, and it can treat only a few diamonds at a time because of the limitation of the processing equipment.
   Scientists are now investigating a new treatment process that reportedly offers significant advantages over the HPHT method. Those who have been working with this process say that it is about half the cost of the HPHT treatment, it can be applied to a larger quantity of diamonds at a single time and, most importantly, it can improve both color and clarity in diamonds. It is known as Low Pressure-High Temperature (LPHT).
   Although the process is not yet available to the commercial marketplace, it is being studied in laboratories in Belgium, the United States and Russia, where the focus is on refining the treatment and coming up with detection protocols to identify diamonds that have undergone LPHT treatment. Any new diamond treatment that enhances a stone’s natural properties is a concern, of course, to an industry where full disclosure is the bedrock of consumer confidence.
   As for its potential impact on the diamond industry, there remains considerable disagreement among scientists. In Belgium, Dr. Katrien De Corte, head of education at the HRD Antwerp lab, is of the opinion that LPHT’s effectiveness is, like HPHT, limited to type II diamonds. But, in Russia, Dr. Alexander Bulatov of the Russian Academy’s Institute of Biochemical Physics, believes LPHT has the potential to improve color and clarity in all diamonds.
   “Its application to natural diamonds is limited because it can only be used with type II diamonds, which includes all Chemical Vapor Deposition (CVD) synthetic diamonds but only about 1 percent of natural diamond production,” says De Corte. In Dr. Bulatov’s opinion, the new treatment has much more far-reaching implications for the industry. “In my opinion,” he told Rapaport Magazine, “LPHT will be very useful for the diamond industry because with it, we could seriously improve color and clarity of all diamonds, natural as well as CVD diamonds.”
   In exclusive interviews, Rapaport Magazine spoke recently with both Dr. De Corte and Dr. Bulatov.

Rapaport Magazine: What is LPHT?
Katrien De Corte: LPHT is a color treatment procedure that stands for Low Pressure-High Temperature. Just like HPHT, the LPHT treatment aims to decrease brown color in type II diamonds. We first heard about it in 2008 when a group of nine researchers at the Carnegie Institution of Washington, in Washington, D.C., published their findings in the online edition of the Proceedings of the National Academy of Sciences.

RM: What were their findings?
KDC: They reported that CVD lab-grown diamonds had been successfully annealed at temperatures up to 2200° C and pressures less than 300 torr. The crystals were treated in a hydrogen environment using microwave plasma techniques for periods of time ranging from minutes to a few hours.

RM: How is this different from HPHT?
KDC: Diamond treatments previously required high pressures up to 60,000 atmospheric pressure during annealing and they were expensive and time consuming.

RM: What are the advantages of this new method for the diamond industry?
KDC: LPHT is still very much in its infancy so its financial impact is still uncertain. From a commercial point of view, this could be used with CVD diamonds, which primarily produces brown crystals that are color enhanced afterward.

RM: Does this new treatment — and its potential for improving the color and clarity of synthetic diamonds — pose any threat to the natural diamond industry?
KDC: As far as we know, there are no natural stones in the market that have been LPHT treated. We expect that in the future, LPHT processors will focus on treating CVD lab-grown diamonds.

RM: Is the LPHT treatment easy to detect?
KDC: HRD Antwerp has been investigating diamonds before and after treatment in order to fully understand the process and to develop conclusive detection criteria. Unfortunately, it is early in the process and details of this investigation cannot be disclosed at this time.

RM: Are there any preliminary actions a diamantaire could take to guard against buying undisclosed LPHT stones?
KDC: We advise everyone to submit all type II stones for investigation by a reputable diamond lab so both their growth origin — natural or lab-grown — as well as the origin of their color — natural or treated color — can be identified. This is all in the interest of full disclosure.

Commercial Potential
   Dr. James E. Butler, a leading scientist with the Russian Institute of Applied Physics and a research associate with the Smithsonian National Museum of Natural History, has been working in collaboration with HRD on a project to test the LPHT apparatus on treating diamonds. So far, he says he has not experimented with polished goods. Butler says that in the future, any commercialization of this treatment would depend on the interest and willingness of investors and partners to become involved.
   At the same time, Dr. Bulatov has been working with a Russian system for creating LPHT diamonds with Dr. Victor Ralchenko and Dr. Andrey Bolshakov under the supervision of Professor Konov Vitaly.
   “I’ve been working in the field of enhancement of different gems since 1992,” says Bulatov. “Our main interest is the fundamental investigation of physical and chemical properties of diamonds during treatment and we started this work together with scientists from Novosibirsk and Alexandrov as early as 1993.
   “Over the past five years, our main interest has been the treatment of diamonds in hydrogen plasma,” says Bulatov. “We got quite interesting results: The natural diamonds we have treated are becoming much clearer.”
   Bulatov suggests there is commercial potential for the research findings but noted that “considering the very expensive equipment required — costing about $500,000 — and the necessity of a very sophisticated scientific team, we have not yet found interested investors in Russia.
   “Let me emphasize that as scientists we’re always in favor of total disclosure. However, the problem is that there’s no reliable method available yet to detect the treatment,” Bulatov told Rapaport Magazine. “Furthermore, the very great advantage of LPHT is the possibility to treat many diamonds in one run. Another benefit is that there’s no need to repolish after treatment. This being said, we believe that, as with all emerging new treatments, science will be subject to regulation in order to safeguard trust and confidence in the market.”

Article from the Rapaport Magazine - May 2014. To subscribe click here.

Comment Comment Email Email Print Print Facebook Facebook Twitter Twitter Share Share