313 Carat Diamond Emerges as World’s Largest D Colour

The Constellation 313 Carat Emerald Cut polished Diamond

Nemesis International on Thursday unveiled a 313 carat diamond that has been certified as the largest D colour polished stone in history.

The emerald shape, VVS1 clarity diamond, known as Constellation 1, is one of eight stones that make up a collection manufactured from the 813 carat Constellation rough, which Nemesis bought in partnership with Swiss jeweler de Grisogono for $63.1 million in 2016. At $77,613 per carat, the stone still ranks as the most expensive rough diamond ever sold.

Tom Moses, executive vice president and chief laboratory and research officer at the Gemological Institute of America, confirmed with Rapaport News that the stone was the largest graded D colour diamond on record.

However, Nemesis has no immediate plans to sell the diamonds, CEO Konema Mwenenge told Rapaport News on the sidelines of the Dubai Diamond Conference. “We want to showcase this as the work of art that it is,” he stressed. “Diamonds are not just a commodity and this stone is impossible to value. We’re focused on building its legacy.”

The company is considering a roadshow to display the collection around the world at museums and other platforms. “We want to keep them as a family from the same rough,” Mwenenge added. The eight stones vary in size and shape, and range in clarity from flawless to internally flawless and VVS. The second largest stone in the family is a 102 carat diamond.

The diamonds will also be presented in their full polished form for now, but will eventually be mounted into jewelry. That contrasts with the company’s last major project, the Art of de Grisogono, an emerald cut, 163 carat, D flawless diamond, cut and polished in New York from a 404 carat rough diamond. That piece was sold as a necklace that could also transform into a bracelet, fetching $33.7 million at a Christie’s auction.

Source: Diamonds.net

GIA Spots Natural-Synthetic Hybrid Diamond

GIA CVD synthetic diamond

The Gemological Institute of America (GIA) has discovered a synthetic layer that improved the weight and color of a natural diamond, and has warned that the phenomenon may be happening more often.

The cushion modified brilliant, 0.64-carat stone contained about 0.10 carats of chemical vapor deposition (CVD) diamond, the GIA estimated in a lab note last week. The lab-grown layer was greyish-blue, in contrast to the natural section’s yellowish color, giving the combined stone a fancy-greyish-greenish-blue appearance.

This was not the first time a stone of this type has turned up at the GIA: In 2017, it reported on a 0.33-carat, fancy-blue diamond that featured a CVD overgrowth similar to this one.

“With the second of these composites seen at GIA, this could be a new type of product entering the market,” research associate Troy Ardon and analytics technician Garrett McElhenny wrote in the note, which the GIA published in the Spring 2019 issue of its quarterly scientific journal, Gems & Gemology. “The resulting color was likely the main motivation for growing the CVD layer on top of the natural diamond, though the extra weight gained could also be a factor.”

The stone’s unusual nature came to light after testing indicated it had features of both type Ia and type IIb diamonds — a rare combination. It appeared to have absorbed both nitrogen — a feature of type Ia diamonds that gives yellow color — and boron, which is present in type IIb stones and can turn them blue. “Mixed-type diamonds always call for additional scrutiny,” Ardon and McElhenny explained.

The pavilion — the section from the girdle to the bottom — showed natural growth features during fluorescence testing with DiamondView, a De Beers machine for identifying synthetics. However, the crown displayed characteristics of CVD, proving that manufacturers had grown CVD diamond over a natural base. Using computer modeling, the research team was able to calculate the weight of the synthetic part as approximately one-tenth of a carat.

The stone was well disguised: Numerous readings of its photoluminescence showed no indication of any synthetic origin, despite the fact that such tests are usually effective at revealing CVD. This may be because the lab-grown layer was so thin, the note pointed out.

“Natural diamonds with synthetic diamond grown on the surface require extra scrutiny due to the presence of natural-looking features, both spectroscopic and gemological,” the authors continued. “Careful inspection still reveals the presence of synthetic indicators, which expose the true nature of the diamond.”

Source: diamonds.net

GIA Spots Broken Diamond Glued Back Together

Green diamond glued

The Gemological Institute of America (GIA) has identified a stone comprising two halves of a diamond that had been stuck together with an “unknown adhesive.”

Graders noticed a large fracture and cavity on the table of the marquise-cut, 1.38-carat polished diamond submitted to the GIA’s laboratory in Carlsbad, California, for colored-diamond testing. When the gemologists examined the crack under a microscope, they noticed a gap running down the stone from the crown to the pavilion, as well as a slight misalignment in the facets and air bubbles inside the fracture.

The polish lines on the stone’s facets would have linked if there hadn’t been a fracture, GIA gemologist Troy Ardon explained this month in a lab note in the latest edition of Gems & Gemology. For that reason, gemologists determined that the stone had been broken in half after it was at least partially polished, and then repaired with an unidentified adhesive.

“Diamonds have been adhered together with glue to form a diamond-doublet, but a broken diamond that has been repaired was not something previously reported by GIA,” Ardon added.

The GIA couldn’t grade the diamond because the 4Cs wouldn’t apply to it, the note continued. A carat weight would have been meaningless, as it would have comprised the weight of both halves plus the adhesive.

Image: Robison McMurtry/GIA

Source: diamonds.net

Labs Refute Claims HPHT Escaping Detection

IIDGR AMS2 synthetic diamonds test

Major gemological laboratories have rebuffed claims that detection machines are failing to spot synthetic diamonds that have undergone irradiation.

In a trade alert last week, Diamond Services argued that the treatment, generally used to alter the color of a stone, can mask the phosphorescence effect when diamonds created using High Pressure-High Temperature (HPHT) undergo scanning at room temperature.

While detection machines can often identify HPHT diamonds because they phosphoresce — or glow — under ultra-violet light, certain devices fail to spot some of those stones that have been subject to irradiation, the Hong Kong-based diamond-technology company argued.

However, De Beers and the Gemological Institute of America (GIA) have denied the impact of such a phenomenon on their machines’ ability to sift out HPHT synthetics.

“The International Institute of Diamond Grading and Research (IIDGR) confirms that its instruments AMS2, SYNTHdetect, DiamondView and DiamondSure are all effective at screening HPHT synthetic material which has been irradiated and is tested at room temperature,” the De Beers-owned grading unit said in a statement last week.

“Any business using these devices can have full confidence that any such material will be detected without the need to undertake tests at different temperatures,” it added.

Meanwhile, although detection devices based on phosphorescence may not be able to detect some HPHT-grown irradiated synthetics, the GIA’s machines can spot them, the Carlsbad, California-headquartered laboratory stressed.

“The ability of the instruments that GIA uses to differentiate natural diamonds from HPHT and CVD [chemical vapor deposition]-grown synthetic diamonds, including the GIA iD100 gem-testing device and the GIA Melee Analysis Service, is not affected by irradiation treatment,” the GIA told Rapaport News.

Examining diamonds at the temperature of liquid nitrogen can be an extremely accurate method of detecting synthetics, while a technique called Raman spectroscopy is a simple way of spotting irradiated diamonds, according to Joseph Kuzi, founder and president of Diamond Services.

“Our latest findings indicate that the diamond and jewelry trades should show extra caution, but we do not claim that irradiated HPHT-grown synthetic diamonds are undetectable,” Kuzi said.

Source: Diamonds.net

Lab Finds 3ct. Synthetic Diamond with Fake Report

Synthetic diamond with fake report

A grading laboratory in China has discovered a synthetic diamond masquerading as a natural stone, complete with a forged inscription and a falsified report.

The National Gemstone Testing Center (NGTC) in the city of Shenzhen received a round-brilliant, 3.1-carat diamond ring, which it subsequently graded as F or G color and VS clarity, it said last week.

However, when gemologists checked the laser-inscription code that was already on the girdle, using an online certificate-verification service, they found the grading report bearing that number was for a natural diamond with similar, but not identical, characteristics. The certificate they saw online was for an H-color, VS1-clarity diamond.

The Chinese lab carried out tests that confirmed the stone in the ring was synthetic, created using chemical vapor deposition (CVD). The inscription and accompanying paper report, purporting to be from an international grading laboratory, were fakes, the NGTC said.

The stone had a type of impurity, known as a “silicon-vacancy center,” that is extremely rare in natural diamonds but common in CVD diamonds, helping the scientists identify its origins. It also had other characteristics that indicated it was synthetic, such as showing green fluorescence under ultra-violet light.

While this was not the first case of its type — the Gemological Institute of America last year found a synthetic diamond with a forged inscription — it is rarer for a Chinese lab to make such a discovery, NGTC noted. It is also one of the larger synthetic diamonds to have cropped up with false credentials to date, the lab added.

“The growth technology of CVD synthetic diamonds has been making great progress for decades in [terms] of size, color and clarity,” the lab said. “Recently, the distinct characteristics of the synthetic diamond are becoming less, and it is more difficult to differentiate.”

Source: diamonds.net

GIA Unveils Plans for Labs in Surat and Antwerp

Gemological Institute of America (GIA)

The Gemological Institute of America (GIA) will this year open a laboratory in Surat, and expand its operations in Antwerp to include diamond grading.

The GIA has secured premises for the two locations, and expects to open both in the second quarter, it said Monday.

The Surat laboratory will bring the GIA’s services — including its Melee Analysis Service for detecting synthetics — closer to companies in that important manufacturing hub, the organization noted. In Antwerp, it will introduce diamond-grading services, and increase capacity for its mine-to-market (M2M) program, which matches rough diamonds to their resulting polished, the lab said.

“Expanding our facility in Antwerp, and opening a new location in Surat, continues GIA’s mission-driven effort to bring our research-based laboratory services for diamonds, colored stones and pearls ever closer to our clients,” said Tom Moses, the GIA’s executive vice president and chief laboratory and research officer.

Clients will be able to drop off goods for every service at both the Surat and Antwerp labs, the GIA added.

Image: Valerie Power/GIA

Source: Diamonds.net

Synthetic Diamond Fraudulently Inscribed To Match Natural Diamond Report

Fake GIA laser on synthetic diamond

Improvements in diamond growth technology and methods have led to a noticeable increase in colorless synthetic gem diamonds in recent years. Concerns in the diamond industry focus on laboratory-grown diamonds not being properly disclosed or even being sold as natural stones. Through careful examination and analysis, gemological laboratories can separate natural from synthetic diamonds. Occasionally, however, fraud is involved in attempting to conceal a gem’s identity. The Carlsbad laboratory witnessed such an attempt.

On this occasion, a round brilliant cut (figure 1, left) was submitted for an updated diamond grading report. Its girdle was inscribed with an actual GIA report number issued in 2015 (figure 1, right). The older report was for a natural, untreated diamond and contained the following grading information: 1.74 ct, round brilliant cut, D color, Excellent cut grade, and VVS1 clarity. Upon grading, the new submission was described as a 1.76 ct round brilliant cut with F color, Excellent cut grade, and VS1 clarity. Moreover, our screening processes determined that the newly submitted sample needed additional testing to determine its origin. This examination revealed it to be an HPHT-grown synthetic diamond. Synthetic cuboctahedral growth structure and phosphorescence were clearly visible in DiamondView imaging (figure 2).

DiamondView imaging of synthetic growth structure and blue fluorescence.

Figure 2. DiamondView imaging showed the synthetic growth structure and blue phosphorescence typical of HPHT-grown synthetic diamonds.

Aside from the observed discrepancies in weight (1.74 vs. 1.76 ct), color (D vs. F), and clarity (VVS1 vs. VS1), FTIR spectra clearly showed that these were not the same diamond. The natural diamond from the original report was type Ia with aggregated nitrogen impurities, while the new one was type IIb with boron impurities (figure 3). Careful examination of the report number inscribed on the synthetic diamond revealed a font different from the one used by GIA, proving that it was not an authentic inscription.

FTIR absorption spectra of natural and synthetic diamond.

Figure 3. FTIR absorption spectra revealed that the synthetic diamond was type IIb, whereas the fraudulently inscribed report number referred to a natural type Ia diamond. The spectra are offset for clarity.

While most synthetic diamonds that come to the laboratory are properly disclosed, some are submitted out of concern that a stone presented as natural might be synthetic. Rarely do we encounter the type of blatant fraud described here. It is important for the industry and public to exercise caution, because these types of misleading practices do occur. We believe the submitting client noticed inconsistencies with the GIA report information and sent it to the lab for an updated report. If any doubt exists or some aspect of a diamond (such as an inscription) seems odd, the stone should be sent to a gemological laboratory for verification.

Source: GIA Education

Gemmological Institute of America seven week graduate diamond diploma

Gemmological Institute of America

The GIA a gemmological organisation will be conducting a seven week graduate diamond diploma from January 8.

The programme combines theory lessons with practical hands on learning and will be held in Jaipur.

Students will learn how to grade in accordance with the GIA’s 4Cs colour, cut, clarity and carat weight of diamond in the D-Z colour range.  

As well as how to grade diamonds and detect simulants and treatments like fracture filled diamonds using gemmological equipment.

The course will be taught by instructors from the Mumbai campus.

Fraudulent GIA Diamond Certificate Found

The Gemological Institute of America (GIA) has identified and seized a bogus diamond grading report appearing recently in Hong Kong.

In a news release issued on Wednesday, GIA revealed that although the number of the diamond grading report was in existence in their database, it corresponded to a higher-quality diamond with different measurements, colour, and clarity. According to GIA, a lower quality diamond was cut to match the specifications of the diamond that went with the original report. Furthermore, GIA stated that upon closer scrutiny of the false diamond grading certificate, it was discovered that there were several characteristics inconsistent with those found on an authentic GIA diamond grading report, including differences in font, colour, and background.

In the same release, GIA revealed that their investigation had tracked the counterfeit diamond certificate back to Antwerp, Belgium, a major diamond trading center. Information on the perpetrators is now being sought by the GIA, who is working law enforcement authorities around the world to help detect and prosecute such criminal activities. GIA asks that any individuals with information about either this particular bogus certificate or any other fraudulent activity bring it to their attention.

To help both the industry and public, all major laboratories provide an online database service that allows individuals to check the authenticity of a diamond certificate online by entering the diamond report number and the carat weight of the diamond, which then pulls up all available information about the diamond.

However, this online verification service only serves to determine if the certificate number exists, not if the diamond that accompanies it matches the certificate. GIA offers a verification service to confirm the authenticity of a diamond grading report whereby clients must submit both the diamond and certificate to the GIA laboratory.
 
In Australia, DCLA performs this verification service and individuals may bring their diamond and accompanying diamond certificate to the DCLA for verification; please contact the laboratory for more information.