GIA Gem Laboratory Expert Explains Identification Techniques of Natural and Treated Red, Pink Diamonds at AGA Conference

Carlsbad, Calif. – July 12, 2005 – The allure of color and the beauty of diamonds have a powerful appeal for the gem-buying public, and demand for fancy-colored natural diamonds has increased sharply in recent years. Their availability, however, has remained very limited, especially in the highly prized pink-to-red color range. Natural-color diamonds with a dominant red color are some of the most sought-after and typically achieve very high per-carat prices when they come up at auction. The highest price ever paid per carat for a diamond at auction was the 0.95-ct. Hancock Red, which achieved an extraordinary $924,000 per carat.

Even the expanded supply of pink diamonds from the Argyle mine in Australia has not satisfied the public’s growing appetite for these fancy-colored diamonds, and reds have remained just as scarce and sought-after as ever. As a result, a variety of attempts have been made over the years to impart a pink-to-red color in diamonds. This has ranged from rather low-tech coatings to the application of more sophisticated combinations of treatment techniques involving irradiation with low-energy electrons, followed by annealing. Most recently the application of high-pressure/high-temperature (HPHT) technology has provided an additional method to create such color.

Christopher P. Smith, director of Identification Services at the GIA Gem Laboratory in New York, gave a presentation on the identification of treated-color pink-to-red diamonds at a conference organized by the Accredited Gemologists Association (AGA) on June 3 in Las Vegas. The conference was chaired by Antoinette Matlins, a well known gemologist and author.

Lucent Diamonds of Denver, Colo., a longtime producer of HPHT-grown synthetic diamonds and has dealt extensively with the application of HPHT treatments to modify the color of natural and synthetic diamonds.                                                                                            [MORE]

GIA Gem Laboratory Expert Explains Identification Techniques of Natural and Treated Red, Pink Diamonds at AGA Conference (P. 2)

Working in partnership with New Diamonds of Siberia and their Research and Development Manager, Dr. Victor Vins, Lucent has developed a unique multiple-step procedure to treat natural, type Ia diamonds. The result is colors that range from brown to purple and pink-to-red through HPHT annealing, irradiation, and low-pressure annealing at relatively low temperatures. Those diamonds that result in a pink to red color are sold under the trade name “Imperial Red Diamonds.”

Lucent President Alex Grizenko began the conference with a briefing on the history and evolution of the treatment process, also covering future production capabilities and marketing plans. Grizenko pointed out that all Lucent-treated diamonds (other colors besides red are produced) will be fully disclosed, including a laser inscription. Grizenko was joined by Vins, for whom he interpreted, in answering questions about the technology behind the treatment.

Both Grizenko and Vins described some of the complications involved with their treatment procedure as a result of the HPHT conditions – temperature above 2,150ºC and a pressure of 70 kilobars – so Lucent uses primarily higher clarity stones. Those that survive end up with clarity grades in the VS²–SI¹ clarity range, said Grizenko. “Color is usually created at the expense of clarity.” He added that the treated diamonds are cut shallow to maximize their color.

Several of the Lucent diamonds were available for viewing by conference participants, along with natural pink diamonds supplied by Argyle Diamonds, Ltd. Joseph Casella, Argyle’s senior sales executive for Europe and the U.S., led the team of Argyle representatives at the conference.

Smith co-authored an article on treated-color diamonds in the Spring 2005 issue of Gems & Gemology (“Treated-Color Pink-to-Red Diamonds from Lucent Diamonds, Inc.”).

It provides a detailed scientific report on the treatment process, including charts and many photomicrographs illustrating characteristics resulting from the treatment that are used in identification. Grizenko provided Lucent diamonds for use in researching the article and was consulted, along with Vins.                                                                                        [MORE]

GIA Gem Laboratory Expert Explains Identification Techniques of Natural and Treated Red, Pink Diamonds at AGA Conference (P. 3)

“The process used by Lucent is a stable and permanent treatment,” said Smith, “and no residual radioactivity was detected.” He added, “Several standard gemological properties and characteristics, as well as advanced analytical techniques, will readily identify these diamonds as treated-color, natural-origin diamonds.”

Smith explained the distinguishing characteristics of the Lucent Imperial diamonds, based on GIA’s research, and he illustrated with side-by-side photomicrographs and spectra comparing treated-color and natural-color diamonds. These characteristics include etched surfaces, graphitized coating on mineral inclusions, color zoning, strain patterns, fluorescence, visible luminescence, and spectroscopy. A detailed discussion of how these characteristics are used to identify these HPHT treated-color diamonds follows.                                                                             

Etched surfaces: Areas around the girdle/pavilion that had not been repolished after treatment showed evidence of severe etching. This is a clear indicator of HPHT treatment, said Smith. “Etch features were also evident in surface-reaching cleavages or fractures,” he noted, adding that etching creates a coarse or granular appearance on the surface of the stones and along fracture walls.

Graphitized coating on mineral inclusions: “When diamonds are taken to these temperatures and pressures, it is common for the surfaces of the diamond (both external and internal-surrounding included minerals and along fractures) to partially convert to graphite. “The texture, color, and appearance of these inclusions are very characteristic,” said Smith. In addition, the conversion to graphite requires about 30 percent more space, so internally, the resulting pressure it exerts may cause additional stress fractures around included crystals or as extensions of existing fractures,” said Smith.                                                                                      

Color zoning: This is especially useful for identification, said Smith. “Color concentrations are one of the most distinctive characteristics of this treatment.” As he showed several illustrations, Smith said, “Purple and pink-to-red color concentrations often occurred with brown concentrations and regions that were near-colorless.”                                                 [MORE]

GIA Gem Laboratory Expert Explains Identification Techniques of Natural and Treated Red, Pink Diamonds at AGA Conference (P. 4)

 This type of color zoning is not consistent with naturally colored diamonds, Smith said.  He also noted that no color concentrations were observed at the culet.

Strain patterns. Smith said the most commonly banded strain patterns were observed, showing a low degree of internal strain. Some showed a higher degree of strain, with a combination of banded and mottled patterns, he said, while others revealed a high degree of internal strain.

Fluorescence: Another very diagnostic feature for the identification of these treated color diamonds was their characteristic fluorescence reaction to both long-wave and short-wave UV light. The Lucent diamonds exhibited chalky fluorescence to long-wave UV, usually in combinations of yellow, green, and orange. Under short-wave UV, they showed medium to strong orange fluorescence, commonly with weak yellow zones, Smith said.

Visible Luminescence: Smith said prominent green visible luminescence was typical, and it resulted from high concentrations of H3 centers (an absorption feature at 503 nm). Orange-red visible luminescence was also seen, and was caused by the nitrogen-vacancy defect (N-V)^– center positioned at 637 nanometers (nm). Yellow visible luminescence was due to the (N-V)⁰ center positioned at 575 nm.

Spectroscopy: In its research, GIA used several spectrometers to identify the occurrence and concentration of various defect centers to identify the presence of the treatment. These included Raman photoluminescence (PL), Infrared, and UV/Vis/NIR spectroscopy. Within the infrared region, it was shown that the diamonds were originally type Ia, containing nitrogen in various states of aggregation.

The HPHT steps of the treatment process facilitate the de-aggregation of nitrogen defects, resulting in single substitutional nitrogen (Ib component), as well as other defects, while the subsequent high-energy electron irradiation and relatively lower temperature annealing provide a further reconfiguration of defects to produce the necessary color-causing centers, in addition to others that are characteristic of these treatment methods.                                                  [MORE]                 

GIA Gem Laboratory Expert Explains Identification Techniques of Natural and Treated Red, Pink Diamonds at AGA Conference (P. 5)

Low temperature Raman PL and UV/Vis/NIR spectroscopy further revealed a series of strong absorptions of N-V centers at 637 and 575 nm, 594, H3/H4 at 503, and 496 nm, N3 at 415 nm, as well as others, the combination of which Smith indicated has never been found in natural-color diamonds.

Smith said the GIA Gem Laboratory issues a GIA Gemological Identification Report, not a GIA Diamond Grading Report or Diamond Dossier®, for Lucent treated-color diamonds.

Following Smith’s presentation, conference participants examined natural-color and treated-color diamonds using microscopes, a spectroscope, and a UV lamp provided by GIA Instruments. Smith, Grizenko, Vins, and representatives of Argyle assisted and answered questions. All of the diamonds used in the hands-on part of the conference were provided by Lucent Diamonds and Argyle Diamonds

De Beers Signs New Angolan Agreement

July 13, 2005 at 01:00 GMT Please also see the Angola Annual Review, Press Release and Addendum in attached PDF files. The report will be posted on PAC's website on Wednesday, June 29, 2005, at: www.pacweb.org

After a five year legal dispute over a 1991 contract with Angola’s state diamond company, Endiama, De Beers signed a new agreement covering the exploration, mining and marketing of diamonds on June 17, 2005.

The contract covers five years of prospecting for new kimberlites in a 3,000 km2 area of Lunda Norte. If prospecting produces the expected results - and there is every reason to think it will - a joint mining venture with Endiama will result.

The arbitration process has led to a redefinition of relations between the two companies. The original contract encompassed a $50 million loan to develop mines in the Cuango. These were occupied by UNITA 15 months later, and were used to fund arms purchases. However, due to the absence of a force majeure clause in the contract, interest on the loan remained payable. Now, the $50 million repayment will be transformed into investment in the new project. De Beers has acknowledged that it cannot expect the government to restore the much vaster prospecting areas prior to a change in law in 2000. The change in law reduced all concessions to a maximum of 3,000 km2, both for security reasons, and to allow the development of smaller Angolan companies.

Perhaps the most important question is that of diamonds sales to De Beers. De Beers had, under the 1991 contract, the right to buy all diamonds from the Cuango mines, at that point 80 per cent of Angola’s diamond production; these would also help to repay the $50 million loan. This ended in 2000, when Angola changed its sales system and developed the ASCorp single channel, under pressure from the UN to provide a system that ensured the exclusion of UNITA diamonds from official circuits. The new contract with De Beers has no country-wide implications but instead states that a joint venture will be set up between De Beers and Endiama/SODIAM to sell the diamonds found. This is similar to the Alrosa contract where such a joint venture has also been set up to market the production from Catoca and Alrosa ’s new mines.

De Beers’ new prospecting contract is the latest in a series of agreements that will help turn Angola into a major producer from kimberlites, with one mine already operational, one under construction and additional three with prospecting at a relatively advanced point.

BHP Billiton followed up the announcement of the De Beers contract by stating it will remain a major player in the diamond market and is aggressively exploring Angola in search of the world's next big gem deposit. BHP’s partnership with Petra Diamonds at Alto Cuilo is expected by analysts to produce a major diamond discovery.

Two further companies took a more competitive approach to the De Beers/Endiama announcement. New Millennium Resources/Angola Resources Pty. announced that it is bringing forward its exploration programme at its Rio Lapi concession in Angola, by six months, to commence prospecting in June 2005. The company will carry out drilling and analysis of up to eleven magnetic anomalies on its concession, as well as continuing alluvial production, which has now reached full output.

Trans Hex has also increased its operations and announced plans to prospect for kimberlites, having acquired a 39 per cent stake in an Angolan company, Matikara Prestação De Serviços, which holds exploration rights on three alluvial properties in Angola and one with kimberlite exploration rights. Transhex has also acquired a share in the Gango and Luana concessions in Angola. Bulk sampling on both projects will start in the third quarter of 2005. Transhex’s Luarica mine, in which it holds a 35 per cent share, is now producing 95,000 carats a year but will increase production to 168,000 carats in 2006. Fucauma is still being commissioned but at full capacity will produce c 120,000 carats a year.

As it now stands, Angola may have eight kimberlite pipes under development, with at least three being mined, within the next three years, and other discoveries are highly probable. The new De Beers contract does not place De Beers as the most significant player in Angola, but it does aid in consolidating the new direction for diamond mining there.

For more information, please contact:

Great Britain: Christine Gordon (English): +44 207 837 1598 or at + 44 7901 918 043(mobile) Canada: Bernard Taylor (English and French): 1 613 237 6768

Josée Létourneau Administrator / Administratrice

Partnership Africa Canada / Partenariat Afrique Canada 323 Chapel, Ottawa, Ontario, K1N 7Z2, Canada Tel: +1-613-237-6768 / Fax: +1-613-237-6530 www.pacweb.org

June 05,2005

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Stone age craftsmen in China were polishing objects using diamond 2,000 years before anyone else had the same idea, new evidence suggests.

Quartz was previously thought to be the abrasive used to polish ceremonial axes in late stone age, or neolithic, China.

But the investigations of a Chinese-US team of scientists indicate that quartz alone would not have been able to achieve such lustrous finishes.

The team reports its diamond findings in the journal Archaeometry.

Harvard University physicist Peter Lu and colleagues studied four ceremonial burial axes, the oldest of which dates to about 4,500 years ago.

The team used X-ray diffraction and electron microprobe analysis. This determined that the most abundant mineral in the axes was corundum, known as ruby in its red form and sapphire in all other colours.

Hard case

The majority of prehistoric stone objects are traditionally thought to have been fashioned from rocks containing minerals no harder than quartz. But corundum is one of the hardest minerals known to science, second only to diamond.

What the researchers found even more intriguing were the finely polished surfaces of the axes, which reflect an image like a mirror.

To test their ideas, the researchers took a small stone sample from one of the axes, an artefact from the Liangzhou culture, and subjected it to polishing with diamond, alumina and silica, following modern techniques.

Using an atomic force microscope to examine the polished surfaces on a nanometre scale, the scientists found the diamond-polished surface most closely matched the surface from the ancient axe.

Quartz could not have been the abrasive used by the ancient craftsmen.

"Our understanding of the first use of diamond is based on textual evidence from 500 BC in India. But even that - though probably right - is speculative. This is physical evidence a couple of thousand years earlier," Dr Lu told the BBC News website.

"Any experiment does not give you 100% certainty, but this is the only possibility that makes sense."

However, even with the best modern polishing technologies available, the research team could not achieve a surface as flat and smooth as that on the ancient axe. The ancient craftsmen must have used highly sophisticated techniques.

The authors speculate that the use of diamond and corundum abrasives could be linked to an explosion in finely polished jade artefacts during the Chinese neolithic.

The use of corundum could have slashed production times while diamond could have added the finishing touches, they suggest.

Quartz, previously thought to have been the neolithic lapidary's abrasive of choice, is only slightly harder than jade.

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