Publish Year: - Title: Carnegie Scientists Use Diamond Presses to Study Planet Formation Abstract: The Carnegie Institution’s Geophysical Lab uses high-pressure, high-temperature (HPHT) presses for a variety of purposes, including geological research into the earth and other planets, as well as exotic new materials for technological applications. Here, scientists Steve Shirey and Stevce Stefanoski prepare to load an experiment into of one of the lab’s multi-anvil presses. Duncan Pay © GIA, courtesy Carnegie Institution of Washington.

                      To gemologists, the high-pressure, high-temperature (HPHT) press speaks of synthetic diamond growth or newfangled methods of diamond color treatment.

For Valerie Hillgren, a research scientist at the Carnegie Institution of Washington’s Geophysical Laboratory, the presses that create these conditions are a means to another end: studying how the terrestrial planets of our solar system might have formed.

We’re standing in a large machine room Geophysical Laboratory with Hillgren and her colleague, Dr. Steven Shirey, from the Carnegie’s Department of Terrestrial Magnetism.

The air rings with the hum of heavy equipment and the rhythmic tick of incremental pressure building in a myriad of pipes. The smell of oil is strong, and dials line the walls. Around us are four enormous multi-anvil presses—each the size of a small Volkswagen—that researchers use to simulate conditions deep inside the earth or other planets. Each apparatus can bring to bear pressures equal to that at the core of the planet Mercury.

The interiors of these machines can accommodate pressures measured in gigapascals (GPa). They’re capable of 25 GPa, the equivalent of 700 km (435 miles) beneath the earth’s surface. Pressures of this magnitude allow scientists to study rock-forming systems in the earth’s mantle.

Although this sounds impressive, it’s only a fraction of the depth of the earth’s layers: the center of the earth’s core is 6,378 km (3,963 miles) below the surface.

“When you want to start looking at things that happen in the deep earth, well, 25 GPa only gets you to the top of the lower mantle,” says Hillgren.

Just for comparison, the pressure inside the earth’s core is 360 GPa or 3.64 million bar. The pressure at the earth’s surface, about 1 bar, equals 0.0001 GPa.

	HPHT Research

	Valerie Hillgren was able to combine the two subjects she loved, astronomy and geology, into a dream job: studying planetary geology at Carnegie using the Geophysical Lab’s HPHT presses. Pedro Padua © GIA, courtesy Carnegie Institution of Washington.
Hillgren’s work focuses on separation of a planet’s mantle and core, specifically when they start to differentiate into metal-rich and silicate-rich portions. “What we’re looking at is how the chemistry of different elements is partitioned between the mantle and the core of a planet, and how that happens under higher pressure,” she says.

Hillgren tells us that the experiments can run anywhere from a few minutes to a day or two, depending on the objectives. “We usually start out with mixtures of oxides and metals in proportions that we think are reasonable for the compositions of the planets,” she explains, “and we put them inside the capsule and heat it up.”

After sufficient heat and pressure, she notes, “It separates into a metal portion and a silicate portion, and then we recover that and study the chemistry.”

View Gallery

	In this sequence of photos, you’ll take a glimpse at the inner workings of the Geophysical Lab’s multi-anvil presses.
Hillgren adds, “We look at what our results tell us about the materials that must have formed the planets, what sort of conditions must have existed, when the cores segregated, and perhaps also what has happened after the segregation of the core.”

“One of the things we can look at to understand that process is the chemistry of the mantle, which leaves a signature behind from when the metal segregates,” she continues. “So we just try to recreate that by using these presses, here, looking at the conditions in the deep interiors of the planets.”

Currently Hillgren is studying the solar system’s innermost planet: Mercury. “Mercury is a very unusual planet with proportionately a very large metal core compared to other similar terrestrial planets in the solar system—Mars, Earth, and Venus.

“It’s a mystery—why does Mercury have such a large core? Is it the innate chemistry of the planet, or is it some process that happened after the planet formed?”

Hillgren and her colleagues consider the compositions of the various meteorites as potential starting materials for planetary formation: “We have lots of different meteorite classes, and we’re looking to see if any of those make sense to be the starting materials that Mercury was made out of.”

	The Chergach meteorite, of which this is a part, fell in Mali in 2007. It’s representative of a class of meteorites called chondrites. These stony (non-metallic) meteorites have not been modified by melting and are considered pretty close to the starting material for many of the planets. Valerie Power © GIA, courtesy H. Obodda Precious Gems and Minerals.
She explains that they’ll experiment with different pressure and temperature conditions. “If we apply different conditions to materials, do we end up with different compositions of mantles and cores? We look at not just the earth, but other planets.”

We ask Hillgren which presses she uses. With a laugh she tells us she uses them all. “Depends on what pressure I want to go to! Right here is a piston cylinder, which can go to 2–3 GPa—which would be very shallow. The other presses are multi-anvils, where we can go up to 25 GPa if you want to go deeper.

Hillgren says the interesting thing about Mercury is its core-mantle boundary. “So if you want to look at the segregation of the core,” she explains, “it’s only 7 GPa, which makes it a very easy and accessible planet to study using these presses with very routine methods.”

Finally, we ask Hillgren how she became interested in this field. She feels very fortunate things turned out the way they did: “When I was young, I was always interested in astronomy, and once I got into college, I became very interested in geology…In my last year in undergraduate school, they had a course on planetary geology, and for me it was just combining two things that I really loved…outer space and geology.”

To see more on high-pressure research at the Carnegie Institution of Washington’s Geophysical Lab, visit: https://www.gl.ciw.edu/research/high_pressure_research

	Other High-Pressure Research at Carnegie
According to Dr. Steven Shirey, the Carnegie Institution’s Geophysical Lab has long been a leader in high-pressure research. It started with experiments in the early 1900s at much shallower pressure and higher temperature to look at rock-forming mineral systems in the earth. Scientists were looking to gain a basic understanding of their thermodynamics to work out how rocks and magmas form in the deep earth.

Shirey tells us there hasn’t been a lot of work on natural diamonds at the Geophysical Lab, but that there’s likely to be more in the future. Much of the lab’s work has been focused on synthetic diamonds—especially CVD-grown—and experiments into exotic new materials for use as semiconductors and other technological applications.

	Early Research Using the Piston Cylinder
Research in the 1960s used the piston cylinder, a simpler type of high-pressure device. As Shirey describes it, “You have a cylinder, that’s the confining jacket, and there’s an inner ring and then a subsidiary ring and then another ring. These confinement rings are assembled at pressure, so that they can handle the potential expansion as you push the piston.”

	Piston Cylinder

	Dr. Steven Shirey explains the Geophysical Lab’s early forays into the realm of high-pressure, high-temperature research, beginning with the earth’s rock-forming systems.
“The sample goes in a cylinder of various materials with a central region,” he says. “It’s usually some sort of capsule made out of a noble metal—could be gold or platinum, or it could be graphite. And then there’s a bunch of compressible components—could be salt or pyrophyllite—and then a jacket around that.”

Pyrophyllite is a phyllosilicate mineral composed of aluminum silicate hydroxide—Al2Si4O10(OH2)—that’s widely used in high-pressure experiments, both as a gasket material and as a pressure-transmitting medium.

Shirey explains that a resistance heating system goes in through the holes in the cylinder: “When you compress the whole thing, you get the pressure from compression and you get the heating from the application of a voltage across this resistance.”

These devices can get into the 50 kilobar (5 GPa) range or thereabouts, which would be about 150 km (93 miles) inside the earth, he says: “That’s about the top end of a piston cylinder.”

That’s miniscule compared to a multi-anvil press, Shirey says, gesturing at the larger apparatus behind him: “Nonetheless, the early problems attacked with the piston cylinder were basic things—the melting relations of the mantle, the kinds of melts that were formed, and this would simulate a lot of the experimental work you’d see in mantle xenoliths that are brought up in kimberlites.”

	Multi-Anvil Presses
Any work done on natural diamond formation would require use of the multi-anvil presses, which can hold larger volumes of experimental materials, Shirey says. Just like the piston cylinder, scientists can apply a voltage across a resistance to heat the ample to high temperatures to replicate those inside the earth or another planet.

	Multi-Anvil Presses

	In this video, Dr. Shirey shows us the Carnegie lab’s multi-anvil presses and explains their advantages over earlier devices like the piston cylinder.
But multi-anvil presses work in a different way, he says: “Here we have these opposed, cubic pieces that float in a larger containment, and then inside them are boron nitride cubes that then have a cutout in the corner and the sample goes in the corner of the cubes.”

Shirey holds the octahedral sample holder—made from a compound of magnesium and chromium oxides (MgO and Cr2O3)—between his thumb and forefinger. It nests at the center of the eight cubes that might be composed of either boron nitride or tungsten carbide. It’s rather tiny, given the bulk of the press. A diagonal hole pierces the sample holder, and that’s where the actual experiment occurs. Shirey tells, without a hint of irony, that this is a “larger-volume apparatus.”

“The virtue of these guys is that they can go to much higher pressures with a volume that’s big enough to put into an electron microprobe to do a pretty good analysis.” @topic:8


Publish Year: - Title: Coronavirus May Cut Chinese Demand, Diamond Companies See Better Times Abstract: The coronavirus epidemic prompted the management of the Hong Kong Gem and Jewellery Show to move the March event to May, fearing the large crowds it draws may spread the disease. Photo by Russell Shor/GIA

Images of empty commercial streets and shopping malls in China fill the news as the coronavirus spreads throughout the country. The management of the Hong Kong Gem and Jewellery Show has moved the event from early March to mid-May because of concerns about the epidemic. In addition, the Hong Kong government has cut off 10 of 13 entry points at the Hong Kong-mainland border and many flights have been suspended in an effort to slow the spread of the disease.
The impact of this will likely cut deeply into the economies of mainland China and Hong Kong, where stock markets have plunged more than 8% after reopening following the New Year’s break. Mainland tourism accounts for about 70% of Hong Kong’s retail business. Retailers, including jewelry sellers Chow Tai Fook and Pandora, have shut stores throughout the country.
While it is too early to get specific data from retailers and suppliers, gold dealers said demand from China hit “record lows” in the last two weeks of January ‒ usually a time when the New Year boosts sales. On the mainland, the government extended the New Year holiday to keep people home – and home they stayed, with city streets deserted, even in the capital of Beijing. The government has injected some $22 billion into the economy in the form of credit to tide it through the crisis.
The World Health Organization predicts that the virus epidemic is only in its early stages and that it will spread well beyond the affected areas of the country. According to economists, this could have a profound effect on the world economy. Beyond its leading consumer market role, China is an integral part of the global supply chain and prolonged disruptions there could adversely affect many markets around the world, especially electronics which, in time, could slow world economic growth several percentage points. Hyundai, the Korean automaker, announced that it is closing its factories because they have run out of key components from China.
DIAMOND ROUGH
The major diamond producers believe the crisis in the rough market ‒ oversupplies bringing softening prices and cutbacks in bank credit ‒ has eased. Some diamond cutting firms who find their credit restricted and cash flow spotty aren’t so sure, but for now De Beers, Alrosa and others have reopened the spigots.
De Beers’ January cycle of $545 million was 9% higher than the first sale of 2019 and the highest in nine months, reflecting the company’s confidence that the supply overhang that depressed prices and demand last year has abated. Alrosa has not yet announced the results of its Jan. 17-21 sales, but the company stated it believes the diamond market is close to “alignment.”
De Beers’ CEO Bruce Cleaver said in a statement that demand for rough diamonds was up following the fourth quarter holiday season because clients needed to restock. De Beers’ sales plunged by 25% last year.
The company, however, clearly has no plans to go back to business as usual. It has been widely reported that De Beers will be shaking up its client list at the end of the year. While few details have been forthcoming, it is probably a 2020 version of its “fewer, stronger, hands” policy that it adopted following the 1980s crisis, with goods that flow more toward dealers without large factories to support, rather than manufacturers.
De Beers’ criteria for becoming a client, which it calls “demonstrated demand,” basically requires firms to purchase a contracted quantity of rough each cycle during the length of the agreement. Many clients, however, had to defer purchases last year, or even sold goods back to De Beers, because they were unprofitable to cut.
Indeed, the 2019 crisis was hardly the first crisis set off by overstocking ‒ it also happened in 2015 and, of course, 2009-2010, when the world economy itself was in crisis. Even before then, many analysts believed that there was an excess of diamond manufacturing capacity of 20% or more, but with the banks supplying credit, manufacturers could afford to store the excess stones.
Alrosa, the world’s largest producer by volume, stockpiled diamonds last year instead of trying to sell them to over-stretched clients – its rough inventory increased by 33%, according to Alrosa’s latest earnings announcement.
The company’s sales were down 26% by value at $3.27 billion, and 12.4% by volume (33.4 million carats) last year. Its inventory grew by five million carats to 22.6 million – or two-thirds of its 2019 sales volume. The size of Alrosa’s inventory suggests that, ironically, it has taken De Beers’ former role of market custodian, stockpiling goods in slow times.
Rio Tinto, the third largest diamond producer, announced that its diamond production declined 8% to 17 million carats last year as the company shifted production to lower grades in both Diavik (Canada) and Argyle (Australia) – often a strategy to avoid over-production.
While Rio Tinto’s Argyle Mine is known for the few hundred carats of fancy color pink diamonds it produces each year, the majority of the 14 or so million carats it produces are small, lower quality stones that have been under considerable price pressure.
It is encouraging, however, that Rio Tinto wants to stay in the diamond business after Argyle closes at the end of this year and Diavik closes in 2023. It wants to take a 60% stake in the Canadian Orion South project, which is a producer of higher-value diamonds. The deposit could be an important source of Type IIa colorless diamonds.
GOLD JEWELRY
Weakening currencies and slowing economic growth pushed demand for gold jewelry to its lowest point in a decade during the final quarter of 2019, according to the World Gold Council.
The group reported demand in India fell 17% in the final quarter of the year, compared to the same period of 2018. Chinese demand also fell 10% as trade disputes with the U.S. and rising prices took their toll. In addition, young buyers have been shying away from plain gold toward more fashion-oriented designs that use much less of the metal, according to the Council.
In the U.S., demand for gold rose 2%, but that was not enough to offset the declines in India and China.
Global demand for gold from all industries – electronics, financial, medical and investment ‒ fell 1% for the year. @topic:7


Publish Year: 2015 Title: Large HPHT-Grown Synthetic Diamonds Examined in GIA’s Hong Kong Laboratory Abstract: These two large synthetic diamonds were produced using HPHT growth methods by the Russian firm New Diamond Technology. The 4.30 ct specimen on the left has D color and SI1 clarity. On the right is a 5.11 ct sample with K color and I1 clarity. Photo by Ming Yin Poon.

              Over the last decade, the jewelry industry has seen rapid improvement in the quality of synthetic diamond grown by the CVD (chemical vapor deposition) method. Colorless and near-colorless CVD synthetics with sizes up to 3.04 ct, with I color and SI1 clarity, have been reported. GIA’s Hong Kong laboratory recently examined two large synthetic diamonds created using the HPHT (high-pressure, high-temperature) method that demonstrated parallel progress in the two growth technologies. These samples, shown above, were produced in Russia by New Diamond Technology.

The first was a 4.30 ct cushion shape with D color and a clarity grade of SI1, based on three small clusters of metallic inclusions. The other was a 5.11 ct cut-cornered rectangular modified brilliant. It had K color and a clarity grade of I1, the result of a few metallic inclusions and two small fractures in the girdle area. Neither one showed reaction to long-wave UV radiation. When they were exposed to short-wave UV, a medium to strong green-yellow fluorescence was observed. Both showed strong yellow-green phosphorescence lasting more than 20 seconds. One noteworthy feature was the absence of pinpoint inclusions, which are common in HPHT synthetic diamonds and often distributed throughout the crystal.

Absorption spectra in the infrared region demonstrated these were type II diamonds, with no absorption band detected in the one-phonon region (approximately 1350–1000 cm–1) where nitrogen impurities occur. A very weak 2800 cm–1 band was attributed to trace substitutional boron. A higher boron concentration was recorded in the D-color synthetic diamond (7 ± 1 ppb, compared to 1.2 ± 0.2 ppb). Photoluminescence spectra collected at liquid-nitrogen temperature with varying laser excitations revealed an emission doublet at 736.6/736.9 nm from the silicon-vacancy defect, and an 882.7/884.4 nm doublet from the well-known Ni-related defect. Very weak emissions from nitrogen-vacancy centers at 575.0 and 637.0 nm were detected only in the K-color sample. Besides metallic inclusions, another important identification feature of HPHT synthetics is fluorescence. Typical fluorescence patterns showing multiple-sector growth were observed in both samples.

These two diamonds were disclosed as HPHT synthetic when submitted for examination. Tested using the GIA DiamondCheck device, both were referred for further testing. Gemological observations and spectroscopic features confirmed they were HPHT synthetics.

Examination of these improved HPHT synthetic diamonds, the largest synthetic diamonds produced by any method that GIA has examined so far, demonstrated significant progress in this growth technology. In addition to their use as gem materials, crystals of this size have many potential industrial applications. @topic:4


Publish Year: 2015 Title: Two Large CVD-Grown Synthetic Diamonds Tested by GIA Abstract: Figure 1. The I-color 3.23 ct round on the left (9.59–9.61 × 5.83 mm) and H-color 2.51 ct round on the right (8.54–8.56 × 5.43 mm) are the largest CVD synthetic diamonds GIA has tested. Photos by Jian Xin (Jae) Liao.

	The quality and size of near-colorless and colorless synthetic diamonds grown by chemical vapor deposition (CVD) have rapidly improved in recent years due to advances in growth techniques and the introduction of post-growth decolorizing treatments. Near-colorless CVD synthetics have now passed the three-carat threshold. In September 2015, a 3.09 ct sample (I color, VS2 clarity) of unknown provenance was submitted to HRD Antwerp. This was preceded by Pure Grown Diamonds’ announcement of a 3.04 ct synthetic (I color, SI1 clarity) in December 2014.

	GIA’s New York laboratory recently tested two large CVD synthetic diamonds (figure 1) submitted for grading services. These synthetics, weighing 2.51 and 3.23 ct, are the largest CVD-grown diamonds GIA has examined to date. The results of the examination underscore the continued improvements in CVD synthetic diamonds.

	The 2.51 and 3.23 ct round brilliants received H and I color grades, respectively. Microscopic examination revealed pinpoint and black inclusions in both, while small fractures along the girdle were only observed in the 2.51 ct round (figure 2). The 3.23 ct synthetic contained a small black inclusion measuring approximately 125 µm. As a result, SI1 and VS2 clarity grades were given to the 2.51 and 3.23 ct samples, respectively. Both revealed irregular stress patterns with high-order interference colors when viewed under cross-polarized light (figure 3), indicating high levels of strain.

Figure 2. Left: These pinpoint inclusions were observed in the 2.51 ct synthetic diamond. Right: A small black inclusion measuring approximately 125 µm was observed in the 3.23 ct sample. Image widths 4.72 mm (left) and 6.27 mm (right). Photomicrographs by Caitlin Dieck.

Figure 3. Irregular stress patterns were observed under the microscope with cross-polarized light. Both the 2.51 ct (left) and 3.23 ct (right) synthetic diamonds showed high-order interference colors. Image widths 5.76 mm and 6.27 mm, respectively. Photomicrographs by Caitlin Dieck.

	The synthetics showed weak orange fluorescence to conventional short-wave UV and were inert to long-wave UV radiation. Exposure to the deep UV radiation ( 230 nm) of the DiamondView revealed an overall strong red-pink fluorescence attributed to nitrogen-vacancy centers with dislocation bundles that fluoresced violet-blue (figure 4), followed by weak greenish blue phosphorescence. Both samples were characterized by a layered growth structure, suggesting that the crystals were grown using a multi-step technique to maximize their volume. The sharp boundaries between the different growth layers are a result of changes in the fluorescent impurity uptake during the starting, stopping, and restarting of growth. These images clearly revealed that at least five growth layers were applied to produce these large crystals. The patterns suggest that the table of the 2.51 ct samples was cut parallel to the growth layers, while the table of the 3.23 ct synthetics was cut at an angle to the growth layers. The dislocation bundles are seen to propagate through the different growth layers. The formation of the two blue bands of highly concentrated dislocations crossing the table of the 2.51 ct specimens is not understood.

Figure 4. DiamondView imaging of both samples revealed strong red-pink fluorescence superimposed with dislocation patterns that fluoresced violet-blue. A layered growth structure indicating start-stop growth was clearly observed on the pavilion of both. The orientation of the layers reveals that the 2.51 ct sample (top) was cut with its table approximately parallel to the growth plane, whereas the layers intersect the table facet in the 3.23 ct sample (bottom). Images by Caitlin Dieck.

	Infrared absorption spectroscopy in the mid-IR range (6000–400 cm–1) showed no major nitrogen-related absorption in the one-phonon region, which classified both samples as type IIa. No hydrogen-related defects were detected, either. UV-Vis-NIR absorption spectra collected at liquid-nitrogen temperature revealed a smooth increase in absorption from the infrared region to the high-energy end of the spectrum, with a 737 nm peak in both samples and a small absorption peak at 596 nm in the 3.23 ct synthetic. The 737 nm peak is an unresolved doublet at 736.6/736.9 nm attributed to [SiV]–. This center is often inadvertently introduced during CVD growth (P. Martineau et al., “Identification of synthetic diamond grown using chemical vapor deposition (CVD),” Spring 2004 G&G, pp. 2–25; W. Wang et al., “CVD synthetic diamonds from Gemesis Corp.,” Summer 2012 G&G, pp. 80–97) but is rarely observed in natural diamonds, especially using absorption methods. The 596 nm feature is particularly useful for identification purposes, as it has only been reported in CVD synthetic material (Martineau et al., 2004).

	Photoluminescence (PL) spectra acquired with 514 nm laser excitation at liquid-nitrogen temperature revealed a doublet at 596/597 nm, nitrogen-vacancy centers at 575 [NV]0 and 637 [NV]– nm, and [SiV]– at 736.6/736.9 nm for both samples, with the [NV]0/– luminescence dominating. The strength of the [NV]0/– centers was consistent with the red-pink fluorescence colors (figure 4). Although the 596/597 nm doublet is not thought to arise from the same center as the 596 nm feature seen in the absorption spectrum of the 3.23 ct sample, it has only been detected in CVD synthetics, thus revealing the samples’ CVD origin (Martineau et al., 2004). The doublet also indicated that the samples had not undergone post-growth HPHT (high-pressure, high-temperature) processing to improve their color, as the treatment would have removed this feature.

	The distribution of [SiV]– centers was investigated through PL mapping of the 736.6/736.9 nm doublet at liquid-nitrogen temperature using 532 nm laser excitation (figure 5). The distribution was different between the two samples, forming patterns that corresponded directly with their DiamondView images (figure 4). For the 2.51 ct sample, the [SiV]– luminescence decreased along the bands with higher concentrations of dislocation bundles. This may indicate that there are fewer [SiV]– centers in this region, or an increased concentration of defects (either structural or impurity-based) that effectively quench the [SiV]– luminescence. Where the growth layers intersect the table in the 3.23 ct sample, the [SiV]– luminescence appeared to be highest at the start of a layer’s growth, decreasing as the growth progressed. This could mean that the concentration of silicon in the growth gas fell over time, or that the concentration of defects that may quench the [SiV]– luminescence increased during growth. Notably, the concentration of dislocations increased as growth progressed.

Figure 5. PL [SiV]- distribution map maps were collected with 532 nm laser excitation. Left: Less luminescence from [SiV]- centers is observed in two broad bands on the 2.51 ct sample. Right: More intense [SiV]- luminescence is found at the diamond layer boundaries in the 3.23 ct sample. Images by Lorne Loudin.

	Analysis of these two large samples demonstrates that high-quality CVD synthetic diamonds can be produced even without post-growth decolorizing HPHT treatment, marking a significant improvement in CVD growth. Using advanced spectroscopic and fluorescence imaging technologies, it is nevertheless possible to detect low concentrations of impurity centers, allowing conclusive determination of these samples’ synthetic origin. GIA is monitoring the development of laboratory-grown diamonds and conducting research to ensure that we can continue identifying every single synthetic diamond. @topic:4


Publish Year: 2016 Title: Natural Colorless Type IIa Diamond With Bright Red Fluorescence Abstract: Figure 1. This 0.40 ct, D-color type IIa round brilliant diamond showed very bright red fluorescence due to strong emission peaks from the nitrogen-vacancy centers. Photo by Nuttapol Kitdee.

The nitrogen-vacancy (NV) center is produced in nitrogen-bearing diamond through the combination of a single nitrogen atom and a vacancy. It can exist in neutral (NV0) and negatively charged (NV–) states. Using photoluminescence (PL) spectroscopy, NV centers can be detected by the occurrence of zero-phonon lines (ZPL) at 575 nm for NV0 and 637 nm for NV–. In natural type IIa diamonds, the emissions of NV centers are usually weak, and the relative intensity of NV0 (575 nm) is typically stronger than that of NV– (637 nm). As a result, the vast majority of natural type IIa diamonds show blue fluorescence, attributed to the occurrence of defects such as N3 or dislocations, when excited by the short-wave UV radiation of the DiamondView. Recently, however, the Bangkok laboratory examined a natural colorless type IIa diamond that showed very bright red fluorescence due to high concentrations of NV centers.

This 0.40 ct round brilliant diamond received a D color grade and an SI1 clarity grade based on surface-reaching fractures at the girdle and on the pavilion (figure 1). The infrared absorption spectrum confirmed a type IIa diamond with no measurable defect-related absorptions. Microscopic examination with cross-polarized light revealed a relatively strong tatami strain pattern with a weak interference color (figure 2). Further examination with the DiamondView showed that this stone exhibited an unusual red fluorescence (figure 3), similar to that of nitrogen-doped CVD synthetic diamonds. However, the DiamondView images revealed dislocation networks of typical natural type IIa diamond along with a tree-ring growth pattern, which is very rare for natural type IIa diamond but typical for natural type Ia diamond.

Figure 2. Viewing the diamond under cross-polarizing filters revealed a tatami strain pattern with a weak interference color, a characteristic of natural growth. Photo by Charuwan Khowpong; field of view 3.1 mm.

Figure 3. DiamondView images of the 0.40 ct diamond showed red fluorescence, which is unusual for natural type IIa stones. This red fluorescence was related to the intense emissions of the NV centers. Also observed was a dislocation network typical of natural type IIa diamond, along with a tree-ring growth pattern. Photo by Wuyi Wang.
In order to detect any possibility of treatment, we employed PL spectroscopy at liquid nitrogen temperature with several laser excitations. With 514 nm laser excitation, the PL spectrum revealed very strong emission peaks from NV0 (575 nm) and NV– (637 nm) (figure 4). This is very rare in natural type IIa diamonds. The higher intensity of the NV0 emission was observed. For this diamond, short-wave UV excitation close to 230 nm was very effective in exciting fluorescence from the NV–, which has a ZPL at 637.0 nm and its strong side bands at longer wavelengths. Due to the relatively high concentration of the NV– defect, strong red fluorescence was observed.

Figure 4. The photoluminescence spectrum at liquid nitrogen temperature using 514 nm
laser excitation displayed strong emission peaks at 575 and 637 nm due to NV0 and
NV– centers, respectively. In natural type IIa diamonds, the intensity of NV centers is
usually weaker than the diamond Raman peak at 552 nm.
Both spectroscopic and gemological features clearly indicated a natural diamond. The excellent color and the red fluorescence, which is rare for a natural colorless type IIa diamond, make this a notable stone. @topic:4


Publish Year: 2016 Title: CVD Synthetic Diamond Over 5 Carats Identified by GIA Abstract: Figure 1. This 5.19 ct CVD synthetic diamond (10.04 × 9.44 × 6.18 mm, with J-equivalent color and VS2-equivalent clarity) is the largest GIA has identified to date. Photo by Johnny Leung and Tony Leung.

Chemical vapor deposition (CVD) technology has accelerated over the last several years, and the rapidly improving techniques have produced large, high-quality near-colorless and colorless synthetic diamonds. Two samples over 3 carats were reported in early 2016 as the largest CVD synthetics. GIA recently tested a CVD-grown synthetic diamond that weighed over 5 carats, marking a significant milestone.

The 5.19 ct cushion modified brilliant measuring 10.04 × 9.44 × 6.18 mm (figure 1) was submitted to GIA’s Hong Kong laboratory for grading service. The stone was not disclosed as a synthetic diamond. Using the lab’s standard screening and testing processes, it was identified as CVD synthetic. Following examination, a GIA Identification Report was issued and the stone was inscribed on the girdle with the report number and the words “Laboratory Grown,” following GIA’s protocols for undisclosed synthetics.

This is the largest CVD synthetic diamond GIA has examined to date, and the largest reported in the jewelry industry. It had J-equivalent color grade and VS2-equivalent clarity, comparable to a high-quality natural counterpart. Natural-looking internal inclusions such as needles and clouds were the major features (figure 2). Strong graining and a fracture in the table were also clearly observed under the microscope. It is worth noting that black inclusions, often contained in synthetic diamond, were not found in this CVD specimen, which could have been mistakenly identified as natural based on microscopic examination alone. This case therefore highlights the importance of using advanced spectroscopic instruments as well as conventional gemological techniques to ensure an accurate identification.

Figure 2. Needles and pinpoints were the major internal features. Black inclusions, a
common feature of CVD synthetic diamond, were not observed. Photo by Billie “Pui
Lai” Law.
Viewing the sample under a binocular microscope with cross-polarized light revealed irregular birefringence patterns with high-order interference colors, a common feature of CVD synthetic diamond (figure 3). Fluorescence images under the short-wave UV radiation of the DiamondView showed strong red fluorescence with irregularly distributed areas of violet-blue (figure 4). The images also revealed a layered growth structure, indicating a start-stop cycling growth process typical of CVD synthesis. Up to six growth layers basically parallel to the table were identified from the fluorescence features. These multiple growth segments make it possible to grow such a thick sample.

Figure 3. Microscopic examination between crossed polarizers revealed high-order
interference colors, attributed to strong lattice dislocation. Photo by Billie “Pui Lai” Law.

Figure 4. Fluorescence imaging from the DiamondView showed strong red fluorescence
with bundles of violet-blue. Up to six growth layers basically parallel to the table were
revealed. Photo by Billie “Pui Lai” Law.
Infrared absorption spectroscopy identified the sample as type IIa. Except for a very weak absorption at 1332 cm–1, no other absorption features (such as hydrogen-related defects) were detected. Photoluminescence (PL) spectra were collected at liquid nitrogen temperature with various excitation wavelengths. The SiV– doublet at 736.6 and 736.9 nm, a common feature of both CVD and HPHT synthetics and only rarely seen in natural diamond, was observed using 457, 514, and 633 nm laser excitation, suggesting the sample’s synthetic origin. Spectra acquired with 514 nm laser excitation also showed emissions from NV centers at 575.0 nm (NV0) and 637.0 nm  (NV–), with the NV0 center dominating in intensity (figure 5). The occurrence of a weak emission pair at 596.5 and 597.2 nm, in combination with the absence of H3 emission, unequivocally identified this as an as-grown CVD synthetic diamond. No post-growth annealing had been applied to improve its color appearance.

Figure 5. The photoluminescence spectrum acquired with 514 nm laser excitation
revealed strong emissions from NV centers in addition to emissions from SiV–.
Emissions at 596/597 nm indicated that this synthetic diamond was not annealed
after growth.
CVD synthetics are available from several sources. The gemological and spectroscopic features of this 5.19 ct sample are very similar to those GIA has examined from Washington Diamonds (now known as WD Lab Grown Diamonds). As diamond growth techniques continue to advance, we expect to see more high-quality samples, both in size and clarity. @topic:4


Publish Year: 2017 Title: Two Natural Type IIa Diamonds with Strong Phosphorescence and Ni-Related Defects Abstract: Figure 1. DiamondView images of two unusual diamonds (0.18 and 0.30 ct, respectively). Left: Unevenly distributed grayish blue fluorescence and strong blue phosphorescence. Right: Vivid red fluorescence, strong blue phosphorescence, and a dislocation network can be seen in the table. Images by Shi Tang.
Strong phosphorescence under UV excitation is rarely seen in natural diamond and normally limited to hydrogen-rich type Ia or type IaA/Ib chameleons and type IIb diamonds (T. Hainschwang et al., “A gemological study of a collection of chameleon diamonds,” Spring 2005 G&G, pp. 20–35; S. Eaton-Magaña and R. Lu, “Phosphorescence in type IIb diamonds,” Diamond and Related Materials, Vol. 20, No. 7, 2011, pp. 983–989). When seen in other diamond types, an even rarer occurrence, it is shorter and less intense. Recently, the National Gemstone Testing Center (NGTC) in Beijing encountered two natural diamonds that showed extraordinarily strong blue phosphorescence and uncommon fluorescence colors under the DiamondView.

The diamonds weighed 0.18 and 0.30 ct and were both graded as E color. Both were type IIa, with neither nitrogen absorption between 1100 and 1400 cm–1 nor boron-related absorption in their infrared spectra. Magnification and examination with a standard UV lamp showed no abnormal phenomena for natural type IIa diamonds. Instead of the deep blue fluorescence and inert phosphorescence that natural type IIa diamonds typically show in DiamondView imaging, the 0.18 ct diamond emitted unevenly distributed grayish blue fluorescence and strong blue phosphorescence, similar to that of a colorless HPHT synthetic diamond. The 0.30 ct diamond displayed vivid red fluorescence and strong blue phosphorescence, which is unusual for a natural colorless to near-colorless diamond (figure 1). Red fluorescence is rare in natural type IIa diamond and seldom reported (Summer 2016 Lab Notes, pp. 189–190).

Photoluminescence (PL) spectra collected with 532 nm laser excitation at liquid nitrogen temperature revealed something even more interesting. Along with the GR1 center emission at 741 nm typically seen in natural type IIa diamonds, the 883.0/884.7 nm doublet that is related to nickel impurity appeared in both samples’ PL spectra (figure 2). This doublet, often referred to as the “1.40 eV center,” is frequently seen in the {111} growth sectors of HPHT synthetic diamonds produced using Ni-based solvents/catalysts. Ni-related defects are more often seen in natural chameleon and greenish yellow diamonds (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243; Summer 2014 Lab Notes, pp. 151–152) but seldom found in colorless to near-colorless natural diamonds (e.g., Spring 2017 Lab Notes, pp. 95–96). For natural diamonds with such strong phosphorescence, the presence of Ni-related emissions is unusual.

Figure 2. PL spectra of the two samples with 532 nm laser excitation. Both showed weak Ni-related doublets at 883.0/884.7 nm and strong NV centers at 575 and 637 nm, as well as the GR1 center at 741 nm.
The PL spectrum of the 0.30 ct sample also presented an extremely strong NV center at 575 nm, compared to the diamond emission at 572 nm, which explained the reddish fluorescence in the DiamondView image. In each sample’s PL spectrum, the relative intensity of NV0 (575 nm) is significantly stronger than that of NV– (637 nm), another sign of natural origin.

Figure 3. The PL spectrum of the 0.30 ct sample emitted with a 532 nm laser, at higher excitation energy. The NV0 center peak is saturated, and emissions at 648 and 776 nm are clearly seen.
Furthermore, when we exposed the 0.30 ct sample to higher-energy excitation with the 532 nm laser to reveal more subtle features, the PL spectrum showed moderately strong emissions at 648/649 nm and 776 nm (figure 3). According to previous research, PL peaks at 648.2 and 776.4 nm are associated with boron in phosphorescing type IIb natural diamonds (Eaton-Magaña and Lu, 2011). Later studies ascribed the 648.2 nm defect to a boron-interstitial complex, while the 776.4 nm peak was assigned to a B-V complex (S. Eaton-Magaña and T. Ardon, “Temperature effects on luminescence centers in natural type IIb diamonds,” Diamond and Related Materials, Vol. 69, 2016, pp. 86–95). These emissions may partly explain the strong phosphorescence of the 0.30 ct sample. Since they were not detected in the 0.18 ct sample, which also exhibited strong phosphorescence—the same is true of other phosphorescent natural IIa diamonds the authors have encountered before—this cannot be the full explanation.

Despite the synthetic-like luminescence color in DiamondView imaging and the Ni-related emissions in the PL spectra, the samples’ Fourier-transform infrared (FTIR) spectra, UV-visible spectra, PL spectra, features observed under the crossed polarizing microscope, and UV reaction indicated that they are natural instead of synthetic. These two samples demonstrated the diversity of luminescence and spectral features found in natural diamond. Their identification also highlights the importance of a comprehensive understanding of diamond origin. @topic:4


Publish Year: 2018 Title: One Natural Melee Diamond Found in Large Batch of HPHT Synthetic Melee Abstract: Figure 1. Out of a parcel of 1,102 diamond melee received at GIA’s New York lab for testing, 1,092 were identified as HPHT synthetic melee. Photo by Sood Oil (Judy) Chia and Towfiq Ahmed.

Over the last decade, the production methods used to create synthetic diamond melee have improved substantially, along with the quality of the specimens themselves. The increase in the amount of synthetic melee submitted—both disclosed and undisclosed—to GIA’s laboratories for identification has exponentially increased since GIA began offering its Melee Analysis Service in 2016. Parcels of melee are often submitted with a mixture of naturals and synthetics. Typically, a few synthetics are detected in batches of natural melee diamonds, known in the trade as “salting” (e.g., S. Eaton-Magaña and J.E. Shigley, “Observations on CVD-grown synthetic diamonds: A review,” Fall 2016 G&G, pp. 222–245).
GIA’s New York laboratory received a batch of 1,102 melee diamonds with a total weight of 9.67 carats for the melee analysis service. The tested melee ranged from 0.98 to 1.52 mm in diameter. Preliminary testing using GIA’s fully automated screening device referred 1,093 for further testing, while nine were found to be outside of the service criteria. Further analysis using detailed spectroscopic analysis confirmed 1,092 (figure 1) out of the 1,093 to be HPHT synthetics. Fourier-transform infrared (FTIR) absorption spectroscopy performed on the referred melee revealed an absorption band at approximately 2800 cm–1 from trace boron in the diamond lattice, classifying these melees as type IIb (boron-bearing), typical of HPHT synthetic diamonds. Due to the relatively high concentrations of boron, these melee diamonds showed a clear blue hue, which is very different from most of the melee diamonds we have tested.
Further examination using photoluminescence (PL) spectroscopy showed no detectable peaks of nickel, often a catalyst used to grow HPHT synthetic diamonds (e.g., Spring 2017 Lab Notes, pp. 95–96). These spectra were in fact atypical of HPHT synthetic diamonds. Distinctive HPHT growth patterns were observed in the DiamondView (figure 2) along with strong phosphorescence following exposure to short-wave UV radiation (figure 3).

Figure 2. This diamond shows characteristic growth patterns of HPHT-grown material. Photo by Stephanie Persaud.

Figure 3. These HPHT-grown synthetic diamond melee, from the parcel of 1,102 specimens, display strong phosphorescence following exposure to short-wave UV radiation. Photo by Sood Oil (Judy) Chia and Towfiq Ahmed.
One sample out of 1,093 was confirmed as a natural diamond. Infrared absorption spectroscopy indicated this stone was type Ia, with a hydrogen peak at 3107 cm–1. DiamondView imaging displayed a typical blue fluorescence and no detectable phosphorescence, both typical for a natural type Ia diamond.
It is interesting to note that only one natural was found in this parcel of melee. This has been the largest percentage of undisclosed synthetic melee that GIA has seen. The majority of the HPHT synthetic melee had no detectable traces of Ni, demonstrating the importance of advanced testing to identify these melees. @topic:4


Publish Year: 2019 Title: Rough Diamond Crystal with an Unusual Coating of Fake Green “Radiation Stains” Abstract: Figure 1. This 6.49 ct rough diamond with patchy green surface color was submitted to GIA’s Carlsbad laboratory for a Colored Diamond Grading Report. Photo by Diego Sanchez.

Due to their rare occurrence and the environment required to create their color, natural green diamonds are some of the world’s most beautiful and sought-after gems. Most diamonds acquire their color from impurities or defects incorporated into the diamond lattice when the material is hundreds of kilometers deep in the earth’s mantle. But most natural green diamonds are colored by radiation damage that occurs at very shallow depths in the earth’s crust over long periods of time. Commonly accompanying this exposure to radioactive minerals and fluids are surface patches of green or brown color that gemologists call “radiation stains.” These are simply areas of extreme damage to the diamond structure caused by alpha particle radiation. Initially green, they turn brown immediately after exposure to temperatures above 500°C. These surface features indicate that a diamond has been exposed to a source of natural radiation; green stains are commonly associated with naturally colored green diamonds.

Figure 2. The diamond’s patchy green coloration is caused by interlocking platy crystals of chromium oxide, visible with magnification. Photomicrograph by Nathan Renfro; field of view 0.72 mm.

Figure 3. The Raman spectrum (514 nm laser excitation) of the rough diamond’s green coating shows clear peaks from chromium oxide (552 and 613 cm–1) as well as the underlying diamond (1332 cm–1). The specific positions of the chromium oxide peaks suggest the coating has been annealed to ~700°C (Mohammadtaheri et al., 2018).
Recently, GIA’s Carlsbad laboratory examined an interesting attempt to imitate a natural green diamond when a 6.49 ct green crystal was submitted for a Colored Diamond Grading Report (figure 1). The surfaces of the resorbed octahedron were covered by uneven patches of green color. Fourier-transform infrared (FTIR) analysis revealed a typical type Ia diamond with abundant nitrogen and hydrogen impurities. However, the ultraviolet-visible (UV-Vis) spectrum was very unusual and did not show any of the bands that are produced by radiation damage in diamond (e.g., the GR1 defect). Careful examination under magnification found that the green color was not due to radiation stains, but instead to groupings of emerald-green platy crystals, ~40 μm in size, attached to the diamond surface (figure 2). Individual platy crystals could easily be flaked off using tweezers or a pointer probe, but they remained adhered to the surface under normal gem testing situations, including wiping the diamond with a stone cloth. X-ray fluorescence (XRF) analysis indicated high concentrations of chromium, and Raman analysis identified the green plates as chromium oxide (figure 3). The Raman peak positions correlated very well with chromium oxide powder that had been heated to ~700°C to produce a crystallized coating (M. Mohammadtaheri et al., “The effect of deposition parameters on the structure and mechanical properties of chromium oxide coatings deposited by reactive magnetron sputtering,” Coatings, Vol. 8, No. 3, 2018, Article No. 111). A small H1b defect present in the diamond’s FTIR spectrum supports this annealing temperature.
Most colored coatings encountered in the lab are on faceted stones and are pink, orange, red, or blue. The warmer hues are typically created by sputter-coating techniques involving metals and the colder hues by inks or other organic dyes. The use of chromium oxide powder to produce a green coating—along with annealing of the powder to produce crystallized plates that adhere to the rough surface to resemble radiation stains—represents a significant attempt to artificially reproduce the features seen on natural green diamonds. While the unique coating is easily discerned from natural green radiation stains under magnification, this stone is a strong reminder to carefully examine any green diamond, even rough crystals, in order to know exactly what you are buying. @topic:4


Publish Year: - Title: Why are Pink Diamonds Pink?GIA Researchers Dive Deep into their Crystal Structure Abstract: These diamonds are from the 2016 Argyle Pink Tender in New York City. Left to right: 0.64 ct Fancy Deep pink oval, 0.75 ct Fancy Intense purplish pink trilliant, 0.91 ct Fancy Vivid purplish pink oval, 1.30 ct Fancy Intense pink heart, 1.35 ct Fancy Intense purplish pink cushion, 0.80 ct Fancy Vivid pink pear, and 0.45 ct Fancy Vivid purplish pink emerald cut. Courtesy of Argyle Pink Diamonds. Photo by Robert Weldon/GIA

Natural pink diamonds are among the most valuable and rare of Earth’s treasures. Top, vivid-colored stones can bring more than $2 million per carat at major auctions. Such prices come from their rarity as much as their beauty – only a tiny percentage of diamonds have pink color, and only a tiny percentage of these have a rich, vivid color.
Pink diamonds created in a laboratory, however, are quite different from most of their natural counterparts. Manufacturers can’t replicate the way the vast majority of these fancy colored diamonds formed in nature, according to GIA researchers.
Employing GIA’s immense database of more than 90,000 natural pink and related colored diamonds graded between 2008 and 2016, GIA researchers Dr. Sally Eaton-Magaña, senior research scientist; Troy Ardon, research associate; Dr. Karen V. Smit, research scientist; Dr. Christopher M. Breeding, senior research scientist and Dr. James Shigley, distinguished research fellow, produced the most detailed and comprehensive gemological analysis of pink diamonds to date, published in the Winter 2018 edition of the Institute’s quarterly journal, Gems & Gemology.

Natural-color pink diamonds are exceptional treasures. The lead article in this issue, based on GIA’s database of more than 90,000 diamonds in the pink, orangy pink, purple, red, and brown color continuum, summarizes their gemological and spectroscopic characteristics. Shown on the cover is the 18.96 ct Winston Pink Legacy, a Fancy Vivid pink emerald-cut diamond that recently sold at auction for more than $50 million. Winston Pink Legacy courtesy of Harry Winston, Inc. © 2018 Christie’s Images Limited
The sample set of 90,000-plus diamonds includes all those submitted to GIA from 2008 to 2016 with pink as a primary color, and also spans the color hue range from red to purple and saturation range from faint to dark, along with brown diamonds, which share a similar cause of color as pink and related stones. Many of those 90,000 diamonds were small, with low color saturation.
This research confirms that the color of 99.5% of pink diamonds comes from distortion in their crystal structure, not from trace elements, such as nitrogen, which causes yellow color in diamonds or boron, which causes blue. In pink diamonds containing nitrogen, the color is generally concentrated within parallel narrow bands called glide planes, lamellae, or pink/brown graining, depending upon the color. These lines are visible under a microscope and cutters orient them perpendicular to the table to maximize body color.
While many color-producing defects can be introduced through laboratory treatment processes, atomic level distortions in a diamond’s crystal structure created by plastic deformation cannot.
“We know that plastic deformation is associated with the vast majority of diamonds with these colors, but we still do not know the actual atomic structure of the defect causing the color,” says Breeding, who notes that the pink color is caused by a broad absorption band centered at 550 nanometer (nm) in spectroscopic analysis. Spectroscopic analysis is an important gemological tool to measure the impurities and other defects within a diamond (and other gemstones) that give rise to specific absorption peaks or bands in the visible spectrum. The researchers said that there is no known method of replicating plastic deformation with the 550 nm absorption band by a laboratory treatment or growth process.
All fancy colored diamonds submitted to GIA’s grading laboratories are subjected to rigorous analysis to be certain that the colors ‒ and the diamonds themselves ‒ are of natural origin, which makes the GIA database extensively detailed and valuable for research, Shigley said. He added that the team selected a representative sample of 1,000 pink diamonds to examine even more thoroughly for the Gems & Gemology article.

How are Laboratory-Grown Pink Diamonds Created?
There are laboratory-grown pink diamonds in the market, but they are created by three different methods, said Eaton-Magaña.
“The first, and by far the most common, is through irradiating (exposing to radiation) a laboratory-grown diamond that was grown with nitrogen impurities, then subjecting it to moderate temperatures (600°C to 1000°C) afterwards,” she said. “The vast majority of pink and related colors are made using this method.”
This process creates a defect in the crystal lattice (caused by a missing carbon atom adjacent to a nitrogen atom within the lattice) called a nitrogen-vacancy center that is responsible for the color. Eaton-Magaña said a tiny percentage of natural pink diamonds have this nitrogen-vacancy center, which is identifiable by spectroscopic lines at 575 nm and 637 nm.
“These nitrogen-vacancy pinks comprise about one half of one percent of the natural pinks in the GIA database,” she said. They are type IIa diamonds (a rare type of diamond with an exceptionally pure chemical composition: almost all carbon, with negligible amounts of nitrogen or boron) with a very uniform pink color and no visible colored lamellae. These stones are sometimes termed Golconda pinks, but they don’t necessarily have a connection to the Indian mine that closed in the late 18th century.
Generally, she noted, natural nitrogen-vacancy pinks have pale colors, while the laboratory-grown and treated diamonds are more highly colored. Additional testing, such as at a gemological laboratory, is essential to determine the cause of color in such diamonds.
The second method cited by the researchers occurs only in chemical vapor deposition laboratory-grown diamonds (CVD), where a 520 nm spectral band is created during growth that results in an orangy-pink color. GIA has only seen a few of these stones, they say, and the color was not as vibrant as other pink lab-grown diamonds.
The third method, which is even more rare, Eaton-Magaña said, is achieved by adding high amounts of silicon to the CVD growth process which, when exposed to UV illumination, creates reversible color change between the stable pink color and a temporary blue color.

Size and Color Statistics: Are Pink Diamonds Rare?
Of the group of diamonds in this study 47% were unmodified (no other color observed) pink; 28% were purplish pink to pinkish purple; 17% were brownish pink to pinkish brown; 10% were brownish orangy-pink to orangy-pink; 3% were brown; 1% were purple-brown, purple-gray and purple; and 0.9% were red, brown-red or orange red. Of the unmodified pink diamonds, 54% were graded faint to light pink.
While brown diamonds are among the most common fancy colors in nature, the low percentage of them in this group suggests that most are sold into the market without grading reports. The brown color is accompanied by other hues, such as pink or yellow, or the brown stones are treated to produce other colors.
The vast majority of the group (83%), weighed less than one carat, with 56% of them being under one-half carat. The dominant shapes were round (24%), pear (20%), rectangle (16%) and cushion (13%).
The research ‒ the most extensive ever carried out on pink and associated colored diamonds ‒ found that 25% are type IIa, which is much higher than with colorless to near-colorless diamonds (where the percentage is < 5%), Breeding said.
The majority of type Ia pink diamonds (diamond containing clusters or aggregates of nitrogen atoms as impurities in the crystal lattice) almost exclusively come from two sources: Australia’s Argyle mine and Russia, which also happen to be the most prolific and consistent producers of such stones. Type IIa pink and other type Ia pink diamonds come from other sources – such as Tanzania, South Africa, and Brazil – but there is no reported regular production from any mine.
“It’s unusual that these types are from very specific locales, especially because they are so rarely found in other sources,” Breeding noted, adding that because Argyle is the dominant source for highly saturated (colored) pink, purplish-pink and red diamonds; the decline in the numbers of such stones will be substantial after the mine closes next year.
Research Aids Automated Detection of Treatment/Lab Growns
This pink diamond study enables GIA to better understand how these rare and beautiful diamonds formed and the properties that give them their color. The researchers found many new details at the atomic level by analyzing the absorption spectroscopy and photoluminescence data. These findings add to the understanding of these amazing stones – which can enable faster, more accurate identification.
The research from this study reinforces GIA’s development of an upgrade for the GIA iD100® gem testing device that adds a function to accurately screen pink and related color diamonds for treatments and synthetics. @topic:10


Publish Year: - Title: US Consumer Confidence Remains Strong; Alluvial Diamond Tracking and Illegal Gold Abstract: Operations at Alrosa’s Lomonosov deposit in Western Russia. Alrosa, along with De Beers, has drastically reduced sales of rough diamonds to deal with the supply overhang. Photo Russell Shor/GIA

Consumer confidence in the U.S. remained strong in August, despite the volatile stock market and increased costs stemming from the trade war with China, according to The Conference Board, which conducts the monthly Consumer Confidence Survey.
“Consumer confidence was relatively unchanged in August, following July’s increase,” said Lynn Franco, senior director of economic indicators at The Conference Board. “Consumer expectations cooled moderately, but overall remain strong. While other parts of the economy may show some weakening, consumers have remained confident and willing to spend. However, if the recent escalation in trade and tariff tensions persists, it could potentially dampen consumers’ optimism regarding the short-term economic outlook.”
Many economists believe that signs of a recession have been developing, but that positive attitudes of U.S. consumers and their spending, have kept the economy from sliding into it.
RETAIL NUMBERS

Some U.S. independent jewelers, notably at the higher end, have done well this year, but the chains continue to report lackluster results.
Signet group reported a 1% decline in same store sales for the second quarter of the fiscal year, with its Zale Corp. division posting a slight rise, while Kay Jewelers and Jared the Galleria of Jewelry posting respective declines of 3% and 4%. Sales at the Piercing Pagoda, the kiosks selling low-priced jewelry, rose 11% and its online sales, which comprise 12% of the company’s business, rose 4%.
Tiffany & Co. registered a 3% decline in same store sales worldwide and 5% in North America for the first half of the year, with Asia sales falling 1%. The company said it still expects sales will increase by single digits worldwide through the holiday period.
HONG KONG SHOW
The protests in Hong Kong have taken their toll on the region’s retail trade, particularly after the participants disrupted the airports and rail services. Sales of jewelry, watches and luxury goods are down 9% for the first seven months of the year, with steep declines in July – 24% for all retail.
The September Hong Kong Jewellery & Gem Fair will go on as scheduled, but several groups, including the Israel Diamond Manufacturers Association, have asked the organizers to postpone it. In response, the fair is offering hotel deals to lure buyers who may be hesitating to attend.
ROUGH DIAMONDS
Rough diamond sales continue to plummet in the wake of oversupplies and tight financing.
De Beers August cycle sales totaled $280 million – about 40% lower than the August 2018 cycle, but slightly higher than July’s allocation of $250 million – the smallest in four years. De Beers’ sales are down 44% from last year’s levels. In addition to purchase deferments, the company is also buying back certain goods from clients.
In a New York Times interview, De Beers’ CEO Bruce Cleaver called the situation “significant indigestion” caused by the banks’ credit squeeze and difficult geopolitics.
Alrosa was predicting that the market will stabilize once “inventories even out in accordance with market demand,” but its sales ran 35% down through the first seven months of the year; the July allocation was down 50% from the previous year while August rough sales were down 36% from the same period last year. Like De Beers, Alrosa is allowing clients to defer rough purchases until early next year.
The company announced it may trim rough sales 5% to 10% next year if market conditions persist.
ALLUVIAL DIAMOND TRACKING
Artisanal diamond miners in the West African nation of Guinea may see more returns from their diamond finds through a traceable supply initiative developed by a Belgian sustainable development organization in cooperation with the Antwerp World Diamond Center (AWDC). The diamonds produced under this program will be traced from individual miners through vetted supply chains and sold in Antwerp under the auspices of the AWDC.
Such programs are rare for miners of alluvial diamonds because the deposits tend to be spread over wide areas and are difficult to monitor. The deposits are located in the Banankoro region of the country and the Belgian organization, CAP Conseil, has been monitoring production to ensure it conforms to Maendeleo Diamonds Standards introduced by the Diamond Development Initiative (DDI) in April.
The Maendeleo Diamond Standards are made of eight specific principles covering legality, consent and community engagement, human and worker’s rights, health and safety, violence-free operations, environmental management, interactions with large-scale mining and site closure. Each of these principles is comprised of provisions defined by measurable requirements, concrete performance criteria and a list of acceptable audit evidence.
DDI developed the Maendeleo Diamond Standards in consultation with a wide range of stakeholders, including governments, industry and local civil society organizations, as well as artisanal and small-scale diamond miners in four countries of Africa and South America. DDI then conducted pilot projects in Sierra Leone in 2012 and 2013 to field-test the system, and expanded it into a full program in 2014.
ILLEGAL GOLD
Reuters has reported that Swiss gold refiners and a major financial house have identified counterfeit gold bars used in refining – kilo bars with forged Swiss bank markings – in their facilities. The bars are real gold of high fineness, but are believed to be from suspect sources, such as money launderers, criminals and sanctioned regimes.
The report estimates that at least $50 million worth of gold bars have been identified by the refiners and J.P. Morgan, but adds that it is likely that many more have slipped through the checks and into the system. Those who found the counterfeits told Reuters they are very professionally done so there are probably “way, way more” in circulation.
While there is no conclusive evidence of the source of the gold bars, authorities believe they are being made in China and sold to traders in Japan, Hong Kong and Thailand.
A second report, this from the New York Times’ “The Weekly” series, notes that illegally mined gold in Colombia is still entering the market as well. This issue was first reported four years ago. The report described the environmental and social cost of Colombia’s illicit gold mining and noted that two-third of the metal coming from the country went through illegal channels.
This issue is critically important because numerous surveys have shown that consumers increasingly care about the origins of the products they buy. At the GIA Symposium last year and at a GIA-sponsored seminar in Las Vegas last June, top executives from across the industry stressed that ethics and sustainability are now top priorities to maintain consumer trust in their brands and products. @topic:7


Publish Year: - Title: Headwinds Slow 2019 Vegas Business, Lab-grown Diamonds Proliferate Abstract: The JCK Show returned to its original venue, the Sands Convention Center, in 2019. Despite the reduced traffic, exhibitors welcomed the move. Photo by Russell Shor/GIA

The U.S. stock market plunged about 7% in the two weeks leading up to the various Las Vegas shows, which ran from May 30 to June 3, injecting an air of caution into business. All told, jewelry designers and manufacturers of finished jewelry reported decent, if measured, demand, while loose diamond and gemstone dealers said business was down from last year.
Manufacturers said retailers came to buy but were cautious about placing large orders. “‘Let’s wait and see’ was the way a lot of discussions ended,” said one exhibitor in the JCK Plumb Club, an association of larger companies.
Continuing the trends of the past two years, jewelers have been incorporating more colored gems into their lines because they usually cost less than diamonds and often result in higher margins.
Judging by the jewelry designs on display at the shows, rainbows, tutti-frutti and various other wild, splashy color combinations were the major look across most price ranges. Designers favored multi-colored tourmalines, fancy colored sapphires and various colored garnets at the middle and high ends, and dyed glass and quartz in the lower price points.
Colored stone exhibitors at the American Gem Trade Association show, not surprisingly, found more calls for such material this year, especially at the lower end.

Multi-color tourmaline pieces were popular, such as these rings by Caroline at AGTA. Photo by Russell Shor/GIA
Diamond dealers, blunted by economic and political uncertainty; excess inventories, especially in sub-caraters (retailers can have their choice of thousands of such stones from online sources); and banks tightening terms of memo deals, saw less traffic and slower buying at the JCK Show.
To boost demand for diamond jewelry this fall and next year, the Diamond Producers Association (DPA) will begin aggressively targeting women who buy pieces for themselves.
The $10 million campaign #ToMeFromMe will be directed at “older millennial women.”
The DPA noted that spending by women in self-purchased jewelry averaged $1300 last year and represented 32% of U.S. diamond jewelry sales.
Despite slow diamond demand at the show, there were a number of new diamond origin tracking services at the JCK Las Vegas show. In addition to the GIA Diamond Origin Report, De Beers and Alrosa introduced their own mine-to-market diamond tracking; the Cullinan Diamond Report debuted as an identification system to track high-value, previously mined diamonds; and Sarine offered a service charting a diamond’s progress through the cutting processes.

Designers looked increasingly to affordable gems to create a bold look, such as this approximately 20 mm Baltic Amber sphere mounted on to textured silver at the Polish pavilion at JCK. Photo by Russell Shor/GIA
LABORATORY-GROWN DIAMONDS
Although calls for loose, natural diamonds were down this year, talk about laboratory-grown diamonds was even livelier than last year. About 50 companies selling lab-grown diamonds exhibited at the JCK Show, which was substantially up from last year, but prices were significantly lower. This led to intense speculation about where this market was heading.
Much of this talk was addressed at a seminar held by De Beers’ Lightbox, a line of laboratory-grown diamond jewelry the company debuted as last year’s Vegas show.
Emily Condo, brand strategy consultant for Lightbox, reported that a survey showed 44% of consumers still have not heard about laboratory-grown diamond brands and that 37% of consumers incorrectly labeled such diamonds as “simulants.”
She reported that the survey found that a majority of consumers were neutral or favorably inclined toward laboratory-grown diamonds because they offered them a choice, especially toward “lighter” occasions, such as non-romantic gifts and everyday wear. Consumers also expressed strong price resistance as prices rose: 78% said they would not spend more than $1,000 on a laboratory-grown diamond.
Lightbox, which sells its laboratory-grown diamonds for $800 per carat plus the cost of mountings, reported that after a year of selling online, 89% of those sales were for 0.5 total carat weight pieces and of those, 51% were colorless, 27% pink and 22% blue. 68% of purchasers were women buying for themselves, the majority of whom were in the 25-34-year age group.
The company noted that its production was set to reach 200,000 carats a year in the second quarter of 2020 after its factory in Oregon goes online.

A 3.01 ct Fancy Vivid orange diamond offered at JCK Luxury. Demand at the high end was muted this year as retailers took a cautious approach. Photo by Russell Shor/GIA
SOCIAL RESPONSIBILITY AND SUSTAINABLE BUSINESS PRACTICES
How best to meet consumer’s requests to have the most information about where their jewelry comes from was the topic of two industry panel discussions during the shows.
GIA presented “Embracing Sustainability Amid New Consumer Expectations” and the Responsible Jewelry Council (RJC) panel focused on corporate social responsibility and sustainable business practices.
The RJC panel included Gina Drosos, CEO of Signet Group; Jeff Corey, president of Day’s Jewelers, an eight-store chain in Maine; Raj Mehta of Rosy Blue; Eric Jens of Luxury Fintech; Feriel Zerouki, who manages De Beers Ethical Initiatives; Shekar Shah of Real gems, New York; and Iris van Veken, RJC executive director.
Participants agreed that best business practices have to begin internally with employees and customers to ensure they are “ingrained into the company’s DNA” in order to have lasting success.
“People want to believe in a company that has values,” Corey said.
Ethically sourced products occupied much of the discussion, with van Veken stressing that it was a shared responsibility across the entire value chain.
One of the most difficult areas for the incorporation of sustainable sourcing practices is artisanal mining. Shah explained that such miners are the backbone of the colored stone industry, “so they must be well taken care of.”
Zerouki added that, to empower artisanal diamond miners, De Beers developed Gem Fair, a program that gives them the best returns on their diamonds by bringing them all the way into the downstream market.
“Trust and transparency are the new equity,” van Veken stressed. “People want to have confidence that their purchases do some good.”
NEW VENUES
The JCK and AGTA shows operated in new venues this year. The JCK Show returned to the Sands Convention center, while the AGTA Show moved to the Las Vegas Convention Center, alongside the Antique and Estate Jewelry and Watch Show.
Exhibitors generally liked the changes, saying the new venues were much easier to navigate. @topic:7


Publish Year: 2016 Title: Decay Kinetics of Boron-Related Peak in IR Absorption of Natural Diamond Abstract: Figure 1. In response to UV excitation, the IR absorption spectra for a 1.01 ct Fancy gray,
nominally type IIa diamond shows a pronounced peak at 2800 cm–1, associated with
type IIb diamond and boron impurities. The intensity of the 2800 cm–1 peak decays over
several minutes. For the sake of clarity, not all collected IR absorption spectra are shown
here; the peak at 2850 cm–1 is unrelated to boron and is caused by hydrocarbon
contamination on the diamond surface.
Recently, gemologists at the National Gold & Diamond Testing Center in China found that the uncompensated boron peak at 2800 cm–1 in FTIR absorption could be induced by UV excitation and then subsequent decay, similar to the phosphorescence response often seen in type IIb diamonds (J. Li et al., “A diamond with a transient 2804 cm–1 absorption peak,” Journal of Gemmology, Vol. 35, 2016, pp. 248–252).

The Carlsbad laboratory recently received a nominally type IIa, 1.01 ct diamond with Fancy gray color. It was identified as natural and, uncharacteristically, showed a 500 nm band phosphorescence, which is typical for type IIb diamonds (S. Eaton-Magaña and R. Lu, “Phosphorescence of type IIb diamonds,” Diamond and Related Materials, Vol. 20, 2011, pp. 983–989). With UV excitation we recorded the transient 2800 cm–1 absorption (associated with uncompensated boron) observed in type IIb diamonds, and we monitored the peak’s decay (figure 1).

From the calculated area of the 2800 cm–1 absorption peak, we can determine the uncompensated boron (Bo) concentration (D. Fisher et al., “Brown colour in natural diamond and interaction between the brown related and other colour-inducing defects,” Journal of Physics: Condensed Matter, Vol. 21, 2009, 364213). Immediately after UV excitation, the diamond showed blue phosphorescence and the FTIR spectrum changed from a nominally type IIa diamond to a type IIb, with an uncompensated boron concentration of ~70 ppb (figure 2, left). An increase in the 2800 cm–1 peak upon UV excitation was previously recorded in some other type IIb diamonds as well and in a few other nominally type IIa diamonds examined by GIA, but those showed much lower values than this sample with UV excitation, with an initial increase in Bo of ~5 ppb or less. The decay of the 2800 cm–1 absorption band in the diamond studied here was well described by the non-exponential decay model 1/(1+kt), where t is the decay time and k is a constant. This equation fit the absorption decay data better than an exponential decay model or the hyperbolic decay model that describes type IIb diamond phosphorescence, 1/(1+kt)2 (K. Watanabe et al., “Phosphorescence in high-pressure synthetic diamond,” Diamond and Related Materials, Vol. 6, 1997, pp. 99–106).

Figure 2. Left: The uncompensated boron concentration for the IR absorption spectra in figure 1 were calculated and compared against several phosphorescence decay models. Right: The decay of the phosphorescence peak at 500 nm, also induced by UV excitation, was calculated and compared against the accepted model for phosphorescence. The DiamondView image shows the diamond’s blue phosphorescence.
Photoluminescence spectra were collected both with and without UV exposure using 488, 514, and 830 nm excitation. The only distinction observed between the two sets of spectra was the addition of a 3H peak (503.5 nm) when the diamond was exposed to UV radiation. The 3H peak is ascribed as an intrinsic defect containing interstitials and is often observed in PL spectra of type IIb diamonds.

Phosphorescence spectra were also recorded (figure 2, right). As expected based on prior research of diamond phosphorescence, the data did correspond well with the hyperbolic model. When boron impurities are present but are electrically compensated by other defects such as nitrogen, the 2800 cm–1 peak would not be detected and a nominally type IIa diamond would be recorded by IR absorption. However, UV excitation creates a charge transfer effect, temporarily uncompensating some of the boron so that the Bo concentration temporarily increases. This absorption decay of the 2800 cm–1 peak is most dramatic in nominally type IIa diamonds such as this sample, but has also been observed to a lesser extent in type IIb diamonds. There are several unanswered questions regarding the phosphorescence mechanism and decay kinetics in type IIb diamonds, and further study of this absorption decay will help address these issues. @topic:4


Publish Year: 2016 Title: Treated Pink Type IIa Diamond Colored by Red Luminescence Abstract: Figure 1. This 4.29 ct type IIa color-treated diamond was graded as Fancy brown-pink under daylight conditions (left) and appeared Fancy purplish gray under incandescent lighting (right). The color change is due to strong NV fluorescence under UV to blue light exposure and irradiation-related GR1 absorption under incandescent illumination. Photo by Robison McMurtry.
Recently, the Carlsbad laboratory received a 4.29 ct type IIa diamond for color origin determination. In daylight-equivalent illumination, the diamond was color graded as Fancy brown-pink, but under incandescent light it appeared Fancy purplish gray (figure 1).

When exposed to long-wave UV light at 365 nm, the diamond exhibited medium orange fluorescence. Based on photoluminescence (PL) spectroscopy, collected using several lasers, it was identified as a treated diamond that had been subjected to high-pressure, high-temperature (HPHT) annealing, irradiation, and subsequent low-pressure annealing. The PL spectra were dominated by the presence of strong NV centers at 575 and 637 nm, along with a strong GR1 peak, confirming the cause of the diamond’s luminescence as the NV centers.

UV-Vis-NIR absorption spectra were collected at room temperature (figure 2) and at liquid nitrogen temperature inside an integrating sphere for this diamond (along with a 0.48 ct treated pink CVD synthetic that does not show the pronounced color change, for comparison). At liquid nitrogen temperature with the diamond under incandescent illumination, the most prominent feature was the GR1 peak creating the purplish gray coloration, comparable to the blue color generated in many irradiated type IIa diamonds. In daylight-equivalent illumination, the emissions of the NV0 and NV– centers were superimposed on the absorption spectrum, thus influencing the diamond’s color within the yellow to red region of the visible spectrum. Color grading of diamonds includes the effect of fluorescence, and therefore the reported color was Fancy brown-pink.

Figure 2. Room-temperature UV-Vis-NIR absorption spectra were collected on the
4.29 ct treated sample (red trace) and a 0.48 ct treated CVD synthetic (blue trace) with
a color grade of Fancy Vivid purplish pink. While NV-related red luminescence caused
a pronounced difference in color for the 4.29 ct sample, it only produced a minor change
in the treated CVD synthetic. In incandescent light (and with minimal influence of the red
luminescence), the synthetic’s color shifted slightly to Fancy Deep purplish pink. The
pronounced absorption from the GR1 peak (550–750 nm) within the 4.29 ct diamond
accounts for the purplish gray color in incandescent lighting.
While treated diamonds have pronounced UV fluorescence due to NV centers, fluorescence spectra collected at a variety of wavelengths show that the NV luminescence is actually stronger when excitation is from blue light (450–500 nm) than from ultraviolet wavelengths, as in the case of this stone (figure 3). This strong emission stimulated by visible light indicates the diamond is colored by red luminescence in response to blue light and, to a lesser extent, by fluorescence due to the UV component in daylight. Other treated pink diamonds, colored by NV absorption, showed similar excitation spectra (Y. Luo and C.M. Breeding, “Fluorescence produced by optical defects in diamond,” Summer 2013 G&G, pp. 82–97). This red luminescence due to NV centers is comparable to the more commonly noted green transmission luminescence from the H3 centers seen in some yellow diamonds. Such yellow diamonds receive greenish color grades due to the visible influence of the green emission on the perceived color in daylight conditions.

Figure 3. These 3-D fluorescence spectra were collected using excitation from the UV
range through the blue range of visible light (320–520 nm). The corresponding
fluorescence spectra show that the relative intensity is much higher when excited by
wavelengths within the visible region than in the UV region. This indicates that red
luminescence excited by visible light is a greater contributor to the pink color than the
UV-activated fluorescence. The 0.48 ct treated CVD synthetic shown in figure 2
demonstrated identical behavior—refer to Luo and Breeding (2016) for comparable
spectra—and indicates that NV-related luminescence contributes to the graded color
in many pink diamonds that are colored by NV centers. The excitation artifact occurs
when the emission spectrometer scans across the excitation wavelength.
For most treated pink diamonds, red luminescence corresponds with and enhances the pink bodycolor (Fall 2011 Lab Notes, pp. 228–229), much like chromium-related red fluorescence enhances the color of rubies. Since bodycolor closely corresponds to luminescence color for most treated pink diamonds, the color difference between daylight and incandescent light sources is minimal. For example, the 0.48 ct treated pink CVD synthetic diamond (figure 2, blue trace) was color graded as Fancy Vivid purplish pink using a daylight-equivalent light and as Fancy Deep purplish pink under an incandescent light. The NV-related emission, excited by the UV to blue light, brightened the diamond in that viewing environment.

The purplish gray bodycolor for this 4.29 ct treated diamond seen under incandescent light derived from the strong GR1 absorption induced by irradiation. The GR1 intensity, as measured by 633 nm photoluminescence spectroscopy and normalized using the diamond Raman peak, was compared with 20 other treated pink diamonds that did not show a substantial color shift. The GR1 intensity of this diamond was 8 times greater than the average value of the 20 treated pink diamonds and 3.5 times greater than the highest value. The GR1 intensity of this diamond was comparable to irradiated green to blue diamonds. In incandescent light, the red luminescence appeared to provide a minimal contribution, as the modifying hue was purplish (implying a reddish component) and not bluish as one might reasonably expect for an irradiated diamond.

Other diamonds have shown a shift in color grade due to appreciable fluorescence. Examples include the 56.07 ct Tavernier diamond, which displays a brown to pink color shift (Y. Liu et al., “The alexandrite effect of the Tavernier diamond caused by fluorescence,” Color Research and Application, Vol. 23, No. 5, 1998, pp. 323–327), and a few type Ib diamonds with a NV-related color shift from greenish brown to orangy brown (Fall 2011 GNI, pp. 234–235).

Some CVD-grown diamonds also have shown a pink to blue color shift, but due to an entirely different mechanism. In those synthetic diamonds, the color change was caused not by a difference in light sources, but by a temporary charge-transfer effect activated by UV exposure. For those CVD synthetics with a high concentration of silicon impurities, UV exposure precipitated a charge transfer between negative and neutral silicon-vacancy centers. In one CVD specimen, the relative concentrations of SiV– and SiV0 were essentially reversed with UV exposure and thus influenced the color change from its stable color of Fancy brown-pink to a temporary Fancy Intense blue (U. D’Haenens-Johansson et al., “CVD synthetic gem diamonds with high silicon-vacancy concentrations,” Conference on New Diamond and Nano Carbons, May 2015, Shizuoka, Japan).

The 4.29 ct natural diamond noted here was HPHT annealed and irradiated to create the NV centers. It appeared to have been irradiated to a far greater extent than most treated pink diamonds, and as a result it had a significantly higher GR1 intensity (as shown in figure 2 and confirmed with 633 nm PL). This accounts for its purplish gray color in incandescent light. The color change between these two attractive colors, along with its large size, makes this diamond quite unusual and serves to illustrate that the color of treated pink diamonds is assisted by red luminescence. This stone also demonstrates that while multiple treatments can provide for some identification challenges, they can also create some truly intriguing products. @topic:4


Publish Year: 2014 Title: Natural Colorless Type IaB Diamond with Silicon-Vacancy Defect Center Abstract: Figure 1. Emissions from the silicon-vacancy defect at 736.6 and 736.9 nm were detected in this 0.40 ct type IaB natural diamond. Photo by Johnny Leung.

The silicon-vacancy defect, or [Si-V]–, is one of the most important features in identifying CVD synthetic diamonds. It can be effectively detected using laser photoluminescence technology to reveal sharp doublet emissions at 736.6 and 736.9 nm. This defect is extremely rare in natural diamonds (C.M. Breeding and W. Wang, “Occurrence of the Si-V defect center in natural colorless gem diamonds,” Diamond and Related Materials, Vol. 17, No. 7–10, pp. 1335–1344) and has been detected in very few natural type IIa and IaAB diamonds over the past several years.

Recently, a 0.40 ct round brilliant diamond with D color and VS2 clarity (figure 1) was submitted to the Hong Kong laboratory for grading service. It was identified as a pure type IaB natural diamond. Infrared absorption spectroscopy showed low concentrations of the hydrogen peak (3107 cm–1) and N impurities in the B aggregates. Photoluminescence spectra at liquid-nitrogen temperature with 514 nm laser excitation revealed [Si-V]– doublet emissions at 736.6 and 736.9 nm (figure 2), while 457 nm laser excitation revealed the H3 (503.2 nm) emission. DiamondView fluorescence images showed blue fluorescence with natural diamond growth patterns. These gemological and spectroscopic features confirmed the diamond’s natural origin, despite the occurrence of [Si-V]– emissions. No treatment was detected.

Figure 2. The emission peaks at 736.6 and 736.9 nm from the [Si-V]– defect are shown in the type IaB diamond’s photoluminescence spectrum. Identical peak positions are detected in CVD synthetic diamonds.
Examination of this stone indicated that the [Si-V]– defect can occur, albeit rarely, in multiple types of natural diamonds. Therefore, all properties should be carefully examined in reaching a conclusion when [Si-V]– is present. @topic:4


Publish Year: 2014 Title: Long-Term Durability of CVD Synthetic Film on Diamond Abstract: Figure 1. This 0.27 ct diamond with a boron-doped CVD synthetic diamond film on the pavilion received a color grade of Fancy Dark brownish yellowish gray. The distinct color zoning seen in this photo makes it apparent that the diamond has been treated in some way and is not a natural stone. Photo by Robison McMurtry.

In 2005, a thin film (10 µm) of synthetic diamond grown by chemical vapor deposition was deposited on the pavilion of a 0.27 ct natural diamond. The CVD layer was deliberately doped with boron to create a bluish color. No subsequent polishing was performed. Rather than blue, the resulting color was a less desirable gray. This natural diamond with CVD overgrowth was then reset in a ring and worn daily by the author for the next eight years. Recently, this hybrid diamond was removed from its setting for gemological and spectroscopic characterization and to assess the current state of the CVD film.

Well-controlled durability studies have examined non-diamond coatings on diamond (e.g., A.H. Shen et al., “Serenity coated colored diamonds: Detection and durability,” Spring 2007 G&G, pp. 16–34) and nanocrystalline diamond coatings on non-diamond materials (J.E. Shigley et al., “Characterization of colorless coated cubic zirconia [Diamantine],” Spring 2012 G&G, pp. 18–30). To our knowledge, however, none have been performed on CVD diamond films grown on natural diamond. The assessment of this one sample, given the exposure a ring is usually subjected to, can indicate the long-term stability of such coatings on diamond. The expectation was that such films would remain stable, as there is no lattice mismatch in the crystal structure between the CVD synthetic film and the natural diamond. Lattice mismatch and the resulting low cohesion at the diamond/non-diamond interface typically result in moderate to very poor durability.

It was difficult to find evidence of the CVD layer using spectroscopic techniques. FTIR absorption (which generally provides data from the bulk of the diamond) revealed no CVD-specific features, only that the underlying diamond was type Ia. Using PL spectroscopy, which collects data from a limited area, it was difficult to find spectroscopic evidence of the CVD film, even when the PL data were collected in confocal mode. No CVD-related 3123 cm–1 peak was detected in IR absorption, and the silicon peak at 737 nm was not observed in PL. The best evidence of the CVD layer’s continued existence on the diamond was from its unusual appearance in visual observation (figure 1) and microscopic analysis (figure 2). The pavilion also showed electrical conductivity, which provides another indication of the boron doping.

Figure 2. This differential interference contrast image shows the irregular texture of the CVD overgrowth film on the pavilion facets of the 0.27 ct natural diamond. Each facet is a different color, and the boundaries between colors are facet junctions. Image by Nathan Renfro; field of view 246 microns.
By examining the pavilion of the diamond at high magnification, we could assess the condition of the CVD layer after eight years of daily wear. The film was still largely intact, covering the entire pavilion and containing only a few sporadic pinholes. There was no noticeable degradation at the facet junctions. The obvious color zoning in figure 1 that appears to divide the diamond into quadrants is likely due to differences in deposition and boron incorporation rates on the various facets. Recently, the diamond was annealed twice, at 600°C and 700°C for one hour each in a reducing atmosphere, in an effort to make it appear bluer. This treatment changed the color from Fancy Dark brownish yellowish gray to Fancy Dark gray.

As treatments become more sophisticated and move from the laboratory into the trade, the need for accurate detection only intensifies. Nevertheless, such semipermanent films are identifiable and reiterate the need to use both spectroscopic and traditional methods for gemological characterization. @topic:4


Publish Year: - Title: Alrosa Claims Wider Role in Diamond Market with Hong Kong Auction Abstract: The highlights of the Alrosa fancy colored diamond auction in Hong Kong: A 15.11 ct Fancy Vivid orangy yellow with a minimum bid of $1.2 million and an 11.06 ct Fancy Deep purple pink that carried a reserve of $3.3 million. Both diamonds were graded by GIA. Photo Russell Shor/GIA

Alrosa, Russia’s diamond mining and marketing arm, auctioned more than 250 polished fancy colored diamonds for $9 million at a tender sale during the September Hong Kong Gem and Jewellery Fair. While the auction was important, even more significant is that it demonstrates that this once-aloof diamond producer is asserting itself into the world diamond market.

The company, the largest diamond producer by volume and second largest by revenue in 2017, publicized the sale well in advance and signaled that it plans to become more involved in diamond marketing in the future – and become the world’s major source for fancy colored diamonds.

Alrosa took the unusual step of inviting members of the trade and media to view its colored diamond collection in a meeting room in a floor above the show. In the past, it kept sales low key, inviting mainly its own clients to bid on rough and polished diamonds without outside publicity.

Evgeny Agureev, director of Alrosa’s United Selling Organization, the division that sells productions of all of Alrosa’s mines, said this was the first of what will be yearly or twice-yearly auctions of diamonds that “fill the fancy colored diamond gap” after Australia’s Argyle mine closes in 2020 or 2021. He added that the company also is looking into establishing a Russian brand for its diamonds, though those plans remain “very preliminary.”

For many years, Alrosa was a passive, though major, seller of rough diamonds. Like De Beers, it sold its rough through a network of selected clients (Alrosa Alliance) in a series of 10 sales each year, but did little to stimulate demand downstream. The company rarely participated in or contributed to industry marketing initiatives until three years ago when it joined the Diamond Producers Association (DPA). Alrosa only began to contribute in a big way to the DPA last year when it kicked in $25 million, more than one-third of the group’s total marketing budget of $70 million.

Alrosa has also opened new sales offices in New York, where it plans to auction 80 large diamonds later this year, and expanded operations in its other markets.

The highlights of the Hong Kong auction were an 11.06 ct Fancy Deep purple pink that carried a reserve of $3.3 million and a 15.11 ct Fancy Vivid orangy yellow that had a minimum bid of $1.2 million. There were 146 other fancy colored diamonds ranging in weight from just over 1 ct to 26 carats, carrying a total reserve price of $10.3 million. The majority of these were yellow, with some modified by orange or brown. Among the smaller diamonds, there were 48 fancy colored pink diamonds, most weighing between 0.3 ct to 0.5 ct. Several other lots featured smaller goods down to melee sizes in various shades of yellow. Of the 250 diamonds offered, 210 were sold.

Mining at the Lomonosov deposit in Western Russia, an important source of Alrosa’s fancy colored diamonds. Photo Russell Shor/GIA
Agureev noted that Alrosa produces 7,000 to 10,000 carats of fancy colored diamonds each year.

A majority of these fancy colors were extracted from Almazy Anabara, an alluvial operation in northwest Yakutia. An increasing number come from the newly developed Lomonosov deposit in the western portion of the country near the border with Finland. GIA reported on this deposit in the Summer 2016 issue of Gems & Gemology.

Alrosa polishes these diamonds instead of auctioning them as rough in hopes of getting better prices, said Agureev, who noted that Alrosa will polish a larger percentage of fancy colored and “special” (colorless over 10.8 cts in the rough) in the future.

“All of these diamonds were polished in our Moscow facility, where we also do our large (colorless) goods,” he said. “It is more costly [to cut diamonds there] but these goods are much less sensitive to labor costs.”

The 11.06 ct Fancy Deep purple pink diamond came from a 27.27 ct rough and took five and one-half months to process from mine to auction, according to Alrosa’s cutter. He said, in a booklet accompanying the diamond, that he needed to polish 36 millimeter-sized “windows” into the mottled surface of the rough to examine the interior of the stone.

The tender sale was well-attended through the entire show, but the final day was cancelled because of Typhoon Mangkhut, which struck Sept. 16 causing some potential buyers to miss the sale.

Alrosa also auctioned 28 polished colorless diamonds over 5 carats, the highlight being a matched pair of E color round brilliants, weighing 5.18 and 5.19 cts, respectively.

The company produced 39.6 million carats of diamonds last year, 3% higher than 2016’s total of 37.4 million carats. Alrosa’s revenues were $4.3 billion, slightly below 2016’s total of $4.5 billion. @topic:7