Title: The World’s Biggest Diamonds: Windows into the Earth’s Deep Mantle Abstract: For geoscientists and gemologists alike, the origins of large, high-clarity, and relatively pure diamonds, like the Cullinan and the 812.77 ct Constellation on the cover of this issue, have long been an enigma. In a December 2016 Science article, a team of researchers led by GIA’s Dr. Evan Smith provided important insights into how these rare and extraordinary gems form deep in the earth’s mantle.

Natural diamonds are science’s best tools for understanding the depths of the earth.

That article presented evidence that such Cullinan-like, nitrogen-poor “CLIPPIR” diamonds contain high-pressure mineral inclusions that are only stable at depths of 360–750 km (approximately 225–465 miles). By contrast, the bulk of gem-quality diamonds form in the base of continental tectonic plates at depths of 150–200 km (95 to 125 miles). Inclusion-bearing CLIPPIR diamonds constitute only 1 in 10,000 of those submitted to GIA’s laboratories. The inclusions these big diamonds carry—iron-nickel metal with minor sulfur and carbon—truly are a window into the earth’s deeper mantle. In our lead paper, Evan Smith and Wuyi Wang partner with Steven B. Shirey of the Carnegie Institution for Science to build on the landmark Science article. They provide more detail on the key features of these remarkable diamonds as well as data on additional samples.

Our second paper, by Robert Weldon, Cathleen Jonathan, and Rose Tozer of GIA’s Richard T. Liddicoat Library, explores the astonishing work of a multigenerational family of gem carvers: the Drehers of Idar-Oberstein, Germany. The authors focus on the contemporary craft of Gerd Dreher and his son, Patrick, artisans with an unerring ability to channel the spirit of the animals they model from high-quality rough gem minerals and richly patterned agates.

In our third paper, Laura Otter, Oluwatoosin Agbaje, Le Thi-Thu Huong, Tobias Häger, and Dorrit Jacob present the first gemological characterization of Australian akoya cultured pearls using Raman, photoluminescence, FTIR, and UV-Vis spectroscopy. Unlike many other akoyas, these Australian examples are marketed without any post-harvest treatments involving dyes or bleaches.

Next, Jennifer Stone-Sundberg, Timothy Thomas, Ziyin Sun, Yunbin Guan, Zachary Cole, Randy Equall, and John Emmett introduce a set of new reference standards designed to improve the quality of trace element analysis in ruby and sapphire. These standards use corundum substrates rather than the typical silicate glasses produced by the National Institutes of Standards and Technology (NIST). This important paper documents the development of corundum sets with precisely known levels of beryllium, magnesium, titanium, silicon, vanadium, chromium, iron, and gallium using secondary ion mass spectrometry (SIMS).

Stefanos Karampelas, Abeer Tawfeeq Al-Alawi, and Ali Al-Attawi provide a comparison of real-time X-ray microradiography (RTX) units fitted with different detectors. Their analysis demonstrates the superior resolving power of a flat panel detector (FPD) over an image intensifier (II) for interpreting fine detail in a pearl’s internal growth structure.

And to complement our emerald and sapphire charts from Winter 2016 and Summer 2017, we present a new one featuring some characteristic internal features of natural, treated, and synthetic ruby. This chart is from GIA’s team of inclusion specialists, led by Nathan Renfro and John Koivula.

As always, there’s something for every gemological taste in our Lab Notes, Gem News International, and Micro-World sections.

Finally, I encourage you to join us for the 2018 GIA Symposium, October 7–9 in Carlsbad, California. This promises to be an unforgettable learning and networking event. You can register to attend or submit an abstract for an oral or poster presentation at symposium.gia.edu. Source: GIA @topic:7


Title: De Beers Sees Growing Diamond Demand Abstract: The Summer 2017 issue of G&G has several Lab Notes about synthetic diamonds that were identified and analyzed in GIA laboratories this year, including a parcel of melee diamonds, like the ones shown above, submitted to the Mumbai laboratory. Photo by Roxane Bhot.

The second half of 2017 will see slow but steady growth in diamond demand, according to De Beers’ forecast.  The company said that fall diamond jewelry sales in the U.S. are expected to rise modestly, while demand from India and China, which had been depressed, is likely to increase.
Company executives noted that rough prices have begun to rise as demand improves, even as the company has increased its rough sales some 7% by volume this year. The average price of rough sold at its five sights (cycles) was down an average of 12% through the first half of the year. That decline, according to De Beers, was caused by a shift toward smaller and lower quality goods, not a decline in the actual price of rough diamonds, which actually rose 4% on average.
The company said it is on track to produce and sell 32 to 33 million carats of diamonds this year, compared to 30 million carats in 2016.
The figures from the U.S. Department of Commerce support De Beers’ optimism. An uptick in consumer spending helped the U.S. economy pick up speed in the second quarter, to double its growth rate to 2.6%. Consumer spending had been slow for the first several months of the year, as retail figures attest.
Forecasts from the Federal Reserve have the U.S. economy and consumer spending continuing to grow at a modest 2% rate through the remainder of the year. Weak business investment and stagnant wages, however, remain a drag on higher growth.
At the same time, U.S. consumer confidence made a strong jump in July, according to the Conference Board, a research firm that developed the Consumer Confidence Index. The index rose 5 percentage points as consumers grew more optimistic about the economy. The percentage of consumers expecting business conditions to improve over the next six months increased from 20.1% to 22.9%, while those expecting business conditions to worsen declined from 10% to 8.2%.

The GIA iD100 gem screening device, prototype shown above, was introduced earlier this year. GIA staff in Hong Kong used the device to screen for synthetics in a diamond ring set with melee and  a marquise-cut diamond center stone. Photo by GIA

IDENTIFYING SYNTHETIC DIAMONDS
The Summer 2017 issue of Gems & Gemology has several articles in the Lab Notes section about synthetic diamonds identified and analyzed in GIA laboratories this year.
Staff in GIA’s Hong Kong lab recognized that a stone submitted for an update service had very different properties from the original report. The color grade H was found to be far below the D noted on the original report, while the clarity grade IF did not agree with the earlier VVS1 grade. In addition, the diamond’s carat weight did not match the original report. The graders checked the report number inscription and found it had been faked. Further testing revealed the stone to be CVD synthetic with subsequent HPHT treatment.
Two other Lab Notes describe how new GIA instrumentation was used to separate natural diamonds from potentially synthetic stones. Examination using GIA’s Melee Analysis Service of a parcel of 323 colorless to near-colorless melee diamonds confirmed that 219 were natural. Detailed further analysis determined that the parcel contained 101 CVD-produced synthetics. The average weight of the diamonds was .015 carat (ct).
Staff at GIA’s Hong Kong lab used a prototype of the GIA iD100 gem screening device to examine a ring containing 70 melee in addition to a marquise-cut diamond center stone. All but one of the melee passed the test for natural diamond, the other was referred as possible synthetic diamond. Further testing determined that it was an HPHT synthetic diamond.
In the final note, a 0.33 “Fancy blue” diamond was found to have an 80-micron thick CVD coating doped with boron over a near colorless natural diamond. This was the first such CVD overgrowth GIA has encountered.
TRADE
The Russia sanctions bill that was enacted by U.S. Congress recently is unlikely to have a direct effect on Alrosa or Russia’s diamond industry – at the outset at least. The bill targets the country’s natural gas and weapons export industries.
Alrosa executives said the bill would have little effect on its operations because the company does not borrow from European or U.S. banks or source a significant amount of its mining equipment and technology from U.S. companies.
Because the bill allows sanctions to be extended beyond their current scope, however, Alrosa is keeping a wary eye.
“The potential difficulties this (potential sanctions on diamonds from Russia) may cause in our company will be incomparable with the global consequences for the entire international diamond market, including diamond exchanges in Europe and other countries,” Alrosa president Sergey Ivanov said in a press statement.
Alrosa is the world’s largest diamond producer of rough diamonds by volume, accounting for 29%, versus De Beers’ 24%.
Sanctions targeted at specific diamond producing nations in the past – South Africa in the 1980s and recently Zimbabwe – have never been very effective. In addition, the 17% tariffs on polished diamonds entering the U.S. from the then-Soviet Union during the 1960s through the 1980s were largely ignored or circumvented.
A potentially tragic flood at Russia’s Mir diamond mine has left eight miners missing and put the mine on indefinite shutdown while rescue and pumping operations are proceeding.  About 150 miners were rescued after ground water began rushing into the mine’s underground operation.
AUCTIONS
The 1,109 ct Lesedi la Rona diamond is back on the sales block. A year after its owner Lucara Diamond Corp. attempted to auction the stone – the second largest gem quality diamond ever found – through Sotheby’s, the company says it may seek a partner to cut and polish the rough, then divide the sales proceeds according to a pre-agreed percentage.
Lucara values the diamond at $70 million or $63,200 per carat before cutting. At a 40% yield – the average for a very large diamond – the per-carat cost would rise to $105,200, without factoring in labor costs.
No color or clarity estimates have been publicly stated for the Lesedi La Rona, but very large (50 carats and higher) polished D Flawless diamonds have fetched $160,000 to $180,000 per carat, while some with extraordinary provenance, such as Elizabeth Taylor’s stone, have brought a lot more. Source: GIA @topic:8


Title: Diamond Producers Aim for Lower Qualities in Today’s Market Abstract: An array of diamonds of various sizes and qualities at Alrosa’s sorting operation in Arkhangelsk. Sizes and qualities of diamonds are distributed unevenly throughout kimberlite pipes and mining companies have learned to tailor their products according to market conditions. Photo by Russell Shor/GIA

The average value of rough diamonds mined last year took a sharp drop according to the latest Kimberley Process (KP) data.

The KP reports that world diamond production was 134 million carats, which was valued at $12.4 billion in 2016, or just under $92.50 per carat. That is in comparison to 127 million carats valued at $13.9 billion, at $109 per carat, in 2015.

Examining the figures more closely, some of the biggest drops in value came from countries where diamond mining is in the hands of the major, sophisticated operations of De Beers, Rio Tinto and Alrosa, in South Africa, Canada and Russia, respectively.

At the same time, diamond demand in major consumer markets, such as the U.S., China and Japan, has trended toward smaller stones and lower qualities.

This isn’t exactly a coincidence.

The major mining companies like to say they dig and sell whatever nature gives them, but technology has given them a way to tweak nature’s generosity. Information tucked into the annual reports of the major mining companies (De Beers, Alrosa and Rio Tinto) shows that they are doing just that – and concentrating their mining on lower quality areas.

Diamonds are not spread evenly inside even the richest grade kimberlite. In some sections, there may be three carats of rough for every ton of kimberlite mined and crushed. In others, there may be only a half carat. It’s the same with size and quality: one section may yield a high percentage of larger higher quality rough, while other parts of the kimberlite may be sprinkled with a concentration of smaller goods and lower qualities.

Thanks to highly sophisticated computer modeling technology, geologists at diamond mining sites can better pinpoint specific areas by continually taking core samples using the data to model the diamond distribution within the kimberlite pipe and adjust their production accordingly. The makes it possible for the diamond miners to be more profitable. They can keep production going at the most efficient levels, with less stockpiling of goods for which there is slow demand.

A geologist examines core samples extracted from approximately 250 feet within Alrosa’s Arkhangelsk kimberlite pipe. Diamond mining companies take many such samples to determine how the diamonds are distributed within the pipe. Photo by Russell Shor/GIA
Interviews at trade shows – Baselworld and Las Vegas this year and Hong Kong late last year – revealed a definite shift in demand toward smaller diamonds and lower qualities. China, for example, which had not favored SI and I1 clarities, began to embrace them as consumers sought to keep expenses down. Indeed, a recent study by the marketing research firm McKinsey & Co., found that luxury buyers in China have become much more price sensitive and much more knowledgeable in the past few years.

Comparing the two years shows that 2015 was a difficult period for the diamond industry and that rough prices fell by an average of 15% during the first half of 2016. Average production value in Canada and South Africa fell nearly 25% – Canada from $143.52 to $107.18 and South Africa from $192.57 to $150. Russia’s average value fell in accordance with the market, from $101 to $88.7, but officials announced earlier this year that they had begun to concentrate production and sales in lower qualities.

The fall in the average price of Botswana’s diamonds (from $143.73 to $138) was much smaller, mostly likely because of the nation’s dependence on diamond revenues and the huge sway it has over De Beers (it holds a 15% stake) and the fact that De Beers’ largest, cheapest-to-run diamond mines are within its borders.

Diamonds continue to flow from Zimbabwe, but at a much lower rate. Production of just two million carats in 2016 was less than half of 2015, though its $50 per carat value remained unchanged and has so for several years.

The reason for this precipitous drop is that the country’s government expelled four of the six mining companies operating the large Marange deposit after they refused to merge their operations into the state diamond company, Zimbabwe Consolidated Diamond Corp. The government’s offer was a combined 50% stake in the company with shares apportioned to the size of their assets.

The companies refused on the grounds that the shallower areas of the Marange deposit have been depleted and that they would have to bear all of the high investment costs of redeveloping the deposit into deep mining operations, even as yield declines.

Five years ago, the country’s diamond production topped 12 million carats with predictions that it could top 20 million within a few years, but as mining grew more difficult and costly, production fell to just under five million carats, prompting the government, which depends on diamonds for 30% of its revenues, to blame mining companies for the production fall off.

A close up view of piles of diamond rough show how the different colors are sorted. Photo by Russell Shor/GIA
Analyst Edahn Golan recently pointed out the huge rise in production from Democratic Republic of the Congo, from 14.7 million carats to 23.7 million, but that the aggregate value only increased by 7%. He theorizes that the Congo, whose production comes from extensive alluvial diggings as well as a state-run mine, miscounted its production figures.

On the export side, there was very little change, with just under 95% of the rough going to five destinations: 39% to India, 30% to EU/Antwerp, 18% to UAE/Dubai, 4% to Israel and 4% to China. Dubai and Antwerp are transfer centers where mining companies have their sales offices, while China remains the destination for much Zimbabwe rough. This will surely show a decline when the 2017 figures are released next summer. Source: GIA @topic:8


Title: Polki Diamonds: A ‘New’ Fashion Statement from Mogul India Abstract: This three-strand bracelet by Sally Agarwal, London, shows how old-style polki diamonds work well in new jewelry designs. The bracelet contains 87 polki cut diamonds, total weight approximately 11.85 ct. set into 18K gold. Photo courtesy Sally Agarwal

Celebrity jewelry designer Jade Jagger sent many jewelers to their glossaries when she introduced a line of jewels featuring “polki” diamonds a few years ago.

Polki diamonds are, in fact, one of the oldest forms of cut diamonds, originating in India long before Western cutting methods were seen there. They often retain their original rough form and have an unfaceted, polished surface. Although they have remained in use in traditional Indian jewelry designs − mainly fashioned for wedding pieces − Western designers like Jagger, who is based in London, and others have begun to incorporate these classic gems into their pieces.

The appeal, according to another London-based designer Sally Agarwal, “is that they generally are cut to follow the original rough stone so no two are alike and they impart a distinctiveness that makes each piece unique.” There’s another reason she is drawn to these diamonds. “They are very flattering to the wearer because the light they give off is much softer compared to the sparkle of modern cuts.”

A polki cut diamond of approximately 0.5 carats bezel set into a gold and enameled ring by Jade Jagger. Many polki cut diamonds are highly included, which adds to their distinctive look. Photo courtesy of Jade Jagger Studio, London
Many of Jagger’s pieces mix polki diamonds with lapis or sapphire. Agarwal’s pieces blend a traditional Mogul jewel look with floral and geometric motifs.

India is the original source of diamonds, with historical accounts of finding the gems dating back 3,000 years. It was the first major culture to value and wear diamonds and many of the world’s legendary diamonds were unearthed there – the Hope Diamond, Koh-i-Noor, Wittelsbach-Graff, Sancy and Regent are the best known.

British jewelry historian Jack Ogden noted that one of the earliest accounts of gem cutting in India was made by the noted Persian scholar al Biruni, who visited India about 1020 CE and wrote that cutters used emery, a dark granular mineral usually composed of powdered corundum, manganite and possibly spinel or hematite, “for cutting, filing and polishing stones.” Of course emery (ranging 7 to 9 on the Mohs scale), could not facet diamonds (10 on the Mohs scale), so cutters used it to polish the surface of the rough stones.

Ogden wrote that it is not entirely clear whether ancient and medieval Indian cutters knew to use diamond powder for cutting, but noted that as much as 700 years later many Indian cutters were still using emery mixed with oil, so cutting techniques had apparently changed little as well. Most diamonds and gemstones were worked on a stone wheel, set vertically. The polisher pushed and pulled on a bow attached to the wheel, turning it back and forth instead of continuously rotating, while holding the stone to be polished with his other hand.

Portuguese explorer Vasco da Gama is usually given credit for leading the first European expedition to establish regular contact with India in 1490. When John Baptiste Tavernier arrived there 200 years later on his famous voyage, he found a flourishing gem trade, including diamonds. By then, some Indian cutters had learned how to cleave diamonds and apply shallow facets using emery and diamond powder on their polishing wheels, according to Tavernier. He called these Mogul cuts, which generally took the form of near-rectangles with beveled edges, lozenge or uneven oval and pear shapes. The latter two had small, angled facets, according to Ogden. A slight adjustment fashioned a faceted crown on top of a flat base and were called polki cuts.

The following centuries saw a growing trade between the West and India; the royalty who ruled the country’s various principalities became regular patrons of the major European master jewelers. The royals purchased many diamonds cut and polished in Europe, which were the forerunners of modern brilliant cuts.

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Indian and Western cutters had a fundamentally different approach, noted Al Gilbertson, GIA’s manager of cut research in Carlsbad, California.

“Mogul cuts are without any particular facet arrangement and have an irregular and asymmetrical form as the cutter was striving for the maximum size possible, but without what they deemed to be flaws,” he said. “Early European styles wanted to follow the design of an octahedron crystal and then slowly moved towards reflecting light back to the viewer as early as the 15th century. This lead to having a large top facet (the table) and various arrangements of facets on the pavilion designed to reflect light back to the observer.”

By the early 19th century, European cutting techniques were adopted by Indian cutters. They remained loyal to cutting diamonds that stayed close to their natural forms, however, because after at least a thousand years, these traditional cutting techniques had become ingrained into the style of Indian jewels. Today, polki is the name applied to a variety of traditional Indian cuts.

“Polki diamonds are still used in most wedding jewels which are still very traditional,” said Siddhartha Sacheti, of Jaipur Gems, a Mumbai-based retailer. “Usually they are backed with silver foil and enameled at the back in the manner of most traditional Indian jewelry.”

Sacheti also explained that while the look remains similar to diamonds cut in centuries past, manufacturing polki diamonds is as up to date as their round brilliant counterparts. “They are all laser-sawn into slices and then polished or lightly faceted by machine,” said Sacheti.

Because they are usually much less expensive than round brilliants or modern fancies, diamond manufacturers use highly included or cloudy rough that still has good color. “The included stones would have a very low yield if they were made into modern cuts,” Sacheti said.

This Mogul-style necklace, by Amrapalli Jewels in Jaipur, features a large polki cut diamond set inside a carved emerald, surrounded by polki cut diamonds. The necklace also features two cabochon sapphires, cultured South Sea pearls and polki cut diamonds. Photo by Eric Welch/GIA
The lower per-carat prices don’t always translate into lower prices at the shop, said Agarwal, who markets her jewels though her own site, boutiques in London and Mumbai, and luxury websites.

“They can be challenging to work with. First, I often have to wait until I find enough stones that will compliment one another in color and shape,” she said. “Second, there are no pre-manufactured settings. Everything has to be done by hand and it is not easy to find people skilled in that kind of work.”

Contemporary polki diamond jewelry is trending back to its roots. Sacheti has begun to make contemporary-looking polki jewels because millennial buyers in India are “looking both East and West.” Source: GIA @topic:7


Title: Diamond-Bearing Eclogite Xenoliths from the Ardo So Ver Dykes Abstract: Figure 1. These five diamond-bearing eclogite xenoliths from the Ardo So Ver dykes in South Africa ranged in weight from 2.24 to 12.40 grams, with the largest measuring 2.5 centimeters in length. Photo by Kevin Schumacher.

              Specimens of gem diamond crystals in rock matrix are almost never found due to the rigorous processing that occurs during diamond mining. Occasionally, a diamond is found in a sample of the kimberlite host rock that brought it to the surface, but finding a diamond in the rock in which it likely crystallized in the earth’s mantle is extremely rare. When pieces of the mantle break off and are transported to the surface in a kimberlite magma, they are called xenoliths (meaning “foreign rock,” because the mantle rocks are not formed from the kimberlite magma itself).

Recently, five small rock samples containing diamond crystals (figure 1) were sent to GIA Research for examination. The samples were submitted by Charles Carmona (Guild Laboratories, Los Angeles) on behalf of owners Jahn Hohne (Ekapa Mining, Kimberley, South Africa) and Vince Gerardis (an occasional trader and collector of unique diamonds and producer of the television series “Game of Thrones”). The specimens were sourced over 25 years ago from a kimberlite fissure mine located 40 miles (65 km) northwest of Kimberley, South Africa. The So Ver mine is located in a group of narrow kimberlite dykes discovered in the 1940s, known as the Ardo dykes, that intruded into Ventersdorp lavas and overlying Karoo shales (M. Field et al., “Kimberlite-hosted diamond deposits of southern Africa: A review,” Ore Geology Reviews, Vol. 34, 2008, pp. 33–75).

Mineralogical examination using microscopy and Raman spectroscopy revealed that the rocks were composed primarily of garnet and clinopyroxene and would be classified as eclogite xenoliths (figure 2). In simple terms, eclogites are metamorphic rocks, typically created when basaltic crust from the ocean floor is subducted deep into the earth’s mantle where high temperatures and pressures cause chemical reactions that change the basaltic minerals into garnet and clinopyroxene. Eclogites, along with peridotites, are considered the most common mantle host rocks for diamond crystallization. EDXRF chemical analysis of the garnets and clinopyroxenes in these samples showed pyrope mole fractions up to about 49% and jadeite mole fractions up to approximately 31%. These results are consistent with other reported diamond-bearing eclogites (T.F. Fung and S.E. Haggerty, “Petrography and mineral compositions of eclogites from the Koidu Kimberlite Complex, Sierra Leone,” Journal of Geophysical Research, Vol. 100, 1995, pp. 20451–20473).

Figure 2. These five diamond-bearing eclogite xenoliths from the Ardo So Ver dykes in South Africa ranged in weight from 2.24 to 12.40 grams, with the largest measuring 2.5 centimeters in length. Photo by Kevin Schumacher.
The diamond crystals in the xenoliths ranged from 1.5 to 4.0 mm in length, and were transparent and near-colorless to pale yellow (figure 3). They occurred as octahedral and combination forms with no visible resorption. No inclusions were visible within the crystals under 10× magnification. FTIR analysis (using an FTIR microscope in reflected light mode) revealed that all of the diamonds were type Ia with abundant nitrogen impurities. Three of the seven diamonds analyzed showed nitrogen impurities dominantly as A-aggregates in concentrations ranging from approximately 420 to 800 ppm.

Figure 3. Seven transparent, near-colorless to pale yellow gem diamonds (five shown in these photos) were observed in the eclogite samples, ranging in length from 1.5 to 4.0 mm. Photos by Christopher M. Breeding.
The data provided here, along with additional ongoing work, will hopefully shed more light on the temperature, pressure, and depth in the earth’s mantle where the diamonds crystallized. Source: GIA @topic:7


Title: Brazil’s Enigmatic Diamonds, Cuprian Liddicoatite, and Silicon in Corundum Abstract: Welcome to the first Gems & Gemology of 2017! This is an unusually diverse issue, combining Brazilian diamonds, cuprian liddicoatite tourmaline, Japanese jadeite, iris quartz, synthetic zincite, and a short but important contribution on the fundamental role of the element silicon in generating blue color in many fine sapphires.

		The original geologic sources of Brazil’s most valuable diamonds remain elusive...

	In our lead article, authors Darcy Svisero, James Shigley, and Robert Weldon survey Brazil’s diamond deposits. This region has produced a significant number of large rough diamonds. It’s also a source of valuable colored diamonds from predominantly alluvial deposits, but today’s diamond production is small and the original geologic sources remain mostly elusive. Although economically viable kimberlite pipes have been discovered in recent years, the outlook for increased production appears challenging.

	Most researchers assume the bulk of copper-bearing tourmaline on the market today is elbaite, but some is undoubtedly another tourmaline species: liddicoatite. Yusuke Katsurada and Ziyin Sun report on the chemistry of copper-bearing liddicoatite tourmaline submitted to GIA’s Tokyo laboratory. Their study shows elevated gallium and lead content in cuprian liddicoatite, which displays stronger fluorescence under long-wave ultraviolet light than cuprian elbaite due to high concentration of rare earth elements.

	In our third paper, John Emmett, Jennifer Stone-Sundberg, Yunbin Guan, and Ziyin Sun discuss the critical role of silicon in the color of gem-quality corundum. Although the effect of trace elements such as iron, titanium, and magnesium within the corundum lattice is well understood, the chemical interaction of these trace elements is not widely appreciated. The authors demonstrate that silicon’s presence is vital to the process that allows titanium to pair with iron and create blue color in sapphire. To the best of the authors’ knowledge, this topic has not been addressed in the gemological literature.

	Our next paper, by Ahmadjan Abduriyim, Kazuko Saruwatari, and Yusuke Katsurada, covers the history and characteristics of Japanese jadeite and compares this highly valued gem with jadeite from other sources. Their study examines the chemical composition and chromophores of jadeite varieties from the Itoigawa and Omi regions of Niigata Prefecture and the Wakasa region of Tottori Prefecture and compares them with samples from Myanmar, Guatemala, and Russia.

	Next, Xiayang Lin and Peter Heaney analyze iris quartz crystals from geodes in the Deccan Trap basalts of west-central India using scanning and transmission electron microscopy and atomic force microscopy. Their investigation reveals that certain crystal faces exhibit etching, which acts as a diffraction grating to produce iridescence.

	Our final paper, by Ji Zhang, Yujie Gao, and Guanghai Shi, provides a gemological characterization of an intriguing industrial by-product: gem-quality synthetic zincite from foundries in Poland.

	Be sure to investigate our three regular sections: Lab Notes documents GIA staff gemologists’ most recent findings, Micro-World reveals fascinating gemstone inclusions, and this issue’s Gem News International reports on the 2017 Tucson gem shows, including an important update on Ethiopian emerald.

	We offer congratulations to the winners of our 2016 Dr. Edward J. Gübelin Most Valuable Article Award, and thank all of the readers who voted. Don’t forget to take this year’s G&G Challenge, our annual multiple-choice quiz. Thank you for all your support through 2016! Source: GIA @topic:1


Title: Mixing of Natural Diamonds with HPHT Synthetic Melee Abstract: Figure 1. These 23 HPHT-grown synthetic diamond melee, ranging from 0.002 to 0.012 ct, were identified recently at GIA’s Hong Kong lab. Photo by Johnny Leung and Tony Leung.

	In recent years, significant amounts of colorless to near-colorless HPHT-grown synthetic diamond melee have been produced for the jewelry industry. As a result, the separation of natural from synthetic melee diamonds has become increasingly critical. GIA offers melee diamond screening services using conventional gemological techniques and analytical methods such as photoluminescence and infrared absorption spectroscopy. In September 2016, GIA’s Hong Kong laboratory received 135 melee diamonds for identification service (see figure 1). Of these, 131 were confirmed to be HPHT synthetics and four were natural diamonds. It is interesting to find natural diamonds mixed in HPHT-dominated groups as “contamination.”

	The tested melee were colorless to near-colorless round brilliants, ranging from 0.002 to 0.012 ct. Infrared absorption spectroscopy performed on the 131 HPHT synthetics showed they were generally type IIb with a very weak absorption band at ~2800 cm–1 from trace boron in the diamond lattice. Blue phosphorescence with varying intensity was observed under short-wave UV radiation (225 nm) and could be easily detected in the DiamondView (figure 2). In photoluminescence spectroscopy collected at liquid nitrogen temperature, clear emissions from SiV– at 736.6/736.9 nm were recorded using 633 nm laser excitation, and extremely strong Ni-related emissions at 882/884 nm occurred in all 131 synthetic melee. These features are similar to those observed from known HPHT synthetic diamonds from a few sources in China.

	Figure 2. Phosphorescence in an HPHT-grown synthetic diamond melee.

	The four natural diamonds showed no phosphorescence under short-wave UV radiation. When examined in the DiamondView, they displayed blue fluorescence and very weak phosphorescence. Infrared absorption spectroscopy indicated these stones were type IIa, and no trace boron absorption was recorded. In photoluminescence analysis, no SiV– emission was detected. Surprisingly, all four diamonds showed weak Ni-related emissions at 882/884 nm. Their most notable photoluminescence feature was an extremely broad band centered at ~700 nm, which is usually observed in natural diamonds.

	We would expect to find a small percentage of HPHT synthetics mixed in with natural diamond melee, but on a few occasions we have seen the opposite. As GIA launches the melee sorting service, we anticipate that more melee goods will be submitted for natural vs. synthetic diamond testing. Source: GIA @topic:4


Title: Carbon Isotope Studies Reveal Diamond Growth History Abstract: This beautiful 56.2 ct octahedral diamond crystal is from Russia’s Mir pipe. Research into the carbon isotopic composition of diamond promises to reveal much about diamond’s place in the earth’s carbon cycle. Photo by Robert Weldon/GIA; courtesy of Bill Larson, Palagems.com.

                      Dr. Jianhua Wang is a man seeking answers to some very basic questions. They range from the origin of the carbon in diamond, to whether the earth’s oceans are growing or shrinking, to the amount of water present on the moon. He’s a senior research scientist at the Carnegie Institution of Washington’s Department of Terrestrial Magnetism (DTM). There, he and colleagues Dr. Steven Shirey, Dr. Eric Hauri, and select visiting researchers collaborate on diamond-related projects.

Today, we are in the DTM’s ion microprobe lab. Dr. Wang introduces us to the complex machine humming behind him. Called a secondary ion mass spectrometer (SIMS), it occupies most of the large room we’re standing in.

	Dr. Jianhua Wang explains operation of the Department of Terrestrial Magnetism’s sophisticated ion microprobe and its relevance to natural diamond research. He has a sample holder in his hand ready to place into the instrument’s vacuum chamber. Photo by Duncan Pay/GIA, courtesy of Carnegie Institution of Washington.

	The Ion Microprobe Explained
Dr. Wang outlines the “business end” of the ion probe: a compact mass of complex cylinders and pipes that resembles a partially disassembled jet turbine. This area contains the ion gun that bombards the sample and the vacuum chamber that holds it. Beyond this is a long “flight tube” that curves around the walls of the room, through an immense magnet the size of a standard refrigerator, to a series of detectors at the end. It’s a very impressive-looking instrument.

	Ion Microprobe

	Join Dr. Jianhua Wang as he introduces us to the Department of Terrestrial Magnetism’s ion microprobe.

	The Ion Microprobe Explained
Dr. Wang gives us a quick outline of the ion microprobe. He tells us the instrument has a primary ion "gun," which generates an ion beam. An ion is an atom with a positive or negative electrical charge. In this case, it's a positive ion of the rare metal cesium (133Cs).

The primary ion beam passes through a set of electromagnetic lenses, he explains. They focus it to a diameter of 15 micrometers (0.0015 cm), and accelerate it toward the sample in the instrument’s high-vacuum chamber. The impact of the cesium ion beam causes the sample to emit a stream of its own ions in response.

Another set of electromagnetic lenses focus the ions emitted by the sample into a secondary ion beam. It’s this feature that gives the SIMS instrument the first part of its name.
Once the beam has been directed, it’s fed into a mass spectrometer to identify the ions produced by the sample. The mass spectrometer separates the secondary ions by their charge and mass into the different isotopes. For diamond, Dr. Wang typically measures carbon or nitrogen, the predominant trace element in diamond.

The mass spectrometer operates on the principle that two ions with the same mass and charge move in the same path in a vacuum when subjected to the same electromagnetic field. Ions with different mass-to-charge ratios are deflected to some degree. The mass spectrometer separates the ions into different masses and counts them in an array of detectors. A computer screen displays the results.

With this machine, Dr. Wang explains, it’s necessary to change the magnetic field to detect isotopes of different masses: “If you want to measure carbon isotopes and nitrogen isotopes using this machine, you have to do it in two different sessions, because nitrogen is a trace element in diamond and carbon is the major element.”

“So you have a lot of carbon signal,” he says. “You do carbon isotopes in the one session, and you measure nitrogen isotopes and nitrogen concentration in a different session.”

	Carbon Isotope Research Illuminates Diamond’s Geologic History
Of all Dr. Wang’s research, the topics of most particular interest to us are diamond’s place in the earth’s carbon cycle, and the origin of the carbon that makes up the fabric of a diamond crystal.

Dr. Wang’s work is complementary to Dr. Shirey’s. While Dr. Shirey focuses on age dating of tiny sulfide inclusions, Dr. Wang works on isotope studies of the carbon and nitrogen in the polished diamond plates that Dr. Shirey produces before cleaving them to recover the inclusions.

Over the last decade, scientists like Dr. Wang have made major advances in understanding the sources of carbon in diamonds. Carbon occurs as two stable isotopes, 12C and 13C. (An isotope of a chemical element is simply an atom with the same atomic number as that element, but with a slightly different mass, resulting from a different number of neutrons in its nucleus.) At the earth’s surface, 12C is almost a hundred times more abundant (98.9% compared to 1.1%).

There are really only two sources for the carbon in natural diamond. It can either come from carbon that has never left the earth’s mantle, which scientists call “primordial,” or it can be “recycled” carbon that has been released from the mantle and incorporated into organic matter—like bacteria or algae—or subsequently formed carbon-bearing minerals like graphite, or carbon-rich rocks like limestone or marble. These materials have then been carried back into the earth’s mantle by subduction, releasing the carbon for diamond formation.

Broadly speaking, scientists classify natural diamonds into two broad categories depending on their geologic origin. Those that source their carbon from the mantle are peridotitic (P-type), and those that contain subduction-recycled carbon are eclogitic (E-type).

Carbon that has been recycled at the earth’s surface tends to have a much higher proportion of 12C to 13C. That’s because the biochemical reactions that fuel living systems generally favor the lighter isotope of carbon. Depending on whether the diamond originated from mantle carbon or recycled carbon, the ratios might be very different, reflecting its geologic history. Dr. Wang’s ion probe can count the different carbon isotopes in diamond, allowing him to determine the ratio of 13C to 12C.

	Carbon isotope composition tells us a lot about a diamond’s geologic history. This illustration shows the difference between some of the main diamond types. δ13C is the 13C/12C ratio measured against a reference standard and deviating from this standard by 0.1%. Note the negative scale and how eclogitic diamonds extend to much lower δ13C values than peridotitic diamonds; n = the number of analyses. Diamonds sourced from mantle carbon (P-type, top graph) have a relatively restricted range of values. Those sourced from subducted recycled carbon (E-type, second graph from top) tend to have a much wider range, though both overlap. Adapted from Cartigny (2005); see the Winter 2013 Gems & Gemology, figure 21, p. 206
Peridotitic diamonds show a narrow range in carbon isotopic composition (given in the delta notation, δ13C, where 13C/12C is referenced to a standard and expressed in ‰) of –10 to –2 δ13C, with more than 95% falling in the main mantle range of –8 to –2.

Eclogitic diamonds show a much wider δ13C range (from –42 to +3), even though many also overlap the main mantle range.

	Carbon in Diamond

	In this video, Dr. Wang explains the significance of his carbon isotope work and how the results inform our understanding of natural diamond’s origin.
So what can studying the carbon isotopes in diamond tell us? “It’s the deepest aspect of how Earth’s subduction works,” Dr. Wang replies.

He shows us a printout of a cathodoluminescence (CL) image of a diamond plate cut from a crystal with a complex growth history. The printout contains an enlargement of a diamond plate just a few millimeters across.

He tells us that the different colors represent the different concentrations of nitrogen throughout the plate, which are normally invisible without CL. “You can see a multi-growth pattern of the diamond, with variations in the amount of nitrogen, and we can use the ion probe to measure carbon isotopes in different regions.”

Each point sampled by the ion probe appears as a tiny spot 15 micrometers (0.0015 cm) across. Figures next to each spot note the isotope concentrations. Dr. Wang points to the trail of sample points and says, “From this information, we see variation of the carbon isotopes.

“If it changes a lot, we can infer there have been different carbon sources in the fluid from which the diamonds grew. In this case, all the carbon is from the mantle—it’s very close to the primordial composition of mantle carbon isotopes.”

On the other hand, Dr. Wang informs us, “If you see very negative carbon isotope composition—say, -24 δ13C—in most cases, this is carbon of organic origin, so they might be coming from the surface of the earth. This could indicate the subduction of oceanic crust from the surface deep into the mantle.

“This technique can show you where the carbon in a diamond came from,” he continues. “Whether it’s from the top—the surface of the earth—or whether it’s of deep mantle origin.”

View Gallery

	This sequence of images introduces you to one of the key analytical instruments used for diamond-related research at the Carnegie Institution’s Department of Terrestrial Magnetism.

	Superdeep Diamonds from Under Brazil
Dr. Wang refers to his recent research paper from 2012, with the diamond research group from the University of Bristol (UK), where he and his colleagues analyzed some unusual diamonds from Brazil. “We found out some diamonds had a very strong signature of organic origin and that some of the inclusions in them were formed very deep in the mantle, like 800 kilometers deep.

“From these inclusions, we can infer that the (carbon) source is from the earth’s surface, but that the diamonds formed deep in the mantle. So that tells us that the subduction went all the way down to the deep mantle.

“The diamond tells us the history of the carbon coming from the surface, how it went down to the mantle and formed the diamond, and the kimberlite brought them to the surface and we got the diamonds and measured them in this lab.”

Like so much of research, it’s conducted with colleagues, especially in this case with Drs. Shirey and Hauri: “Steve has been measuring the sulfide composition in the diamond to find out when the inclusions in diamonds were formed, and Erik has been measuring water content to see how much water is in the deep mantle,” he says. “It’s a collaboration with other people to get this research done.”

	Capabilities of Carnegie’s Ion Microprobe
Dr. Wang explains that this type of instrument is mostly used by the semiconductor industry to measure the implant of different trace elements into silicon wafers.

	Unique Instrument

	Dr. Wang outlines some of the capabilities of the Department of Terrestrial Magnetism’s ion microprobe and explains why it would be very costly to replace.
“In geological and cosmological science,” he tells us, “we’re using it to do trace element analysis in minerals and rocks, including measurement of water in Martian meteorites, and in moon rocks.”  Additional uses haved used DTM cosmochemists to look at particles actively collected from the tail of comets, interplanetary dust particles that constantly rain down on Earth from outer space, meteorite residues that contain refractory grains made in distant stars outside our solar system, and organic components in meteorites blasted from Mars.

To keep a complex and versatile instrument running at state-of-the-art precision requires considerable institutional resources and a team of users. Besides Dr. Wang and his Carnegie colleagues Drs. Alexander, Hauri, Nittler, and Shirey, there is a bevy of post-doctoral researchers and visiting scientists from around the world who routinely come through the ion microprobe facility. It is an exciting place, indeed.

We can’t resist asking the value of this unique instrument: “When we purchased this instrument, it was about $1.5 million,” Dr. Wang says, gesturing at the French-built core of the machine with its ion gun and sample chamber.

With a sweep of his arm he takes in the rest of the ion probe, with its long flight tube and immense magnet. “This is an in-house development—we spent probably a few hundred thousand dollars, but if you buy a commercial, same-size version of the instrument, it would be like $4 to $4.5 million!”

	Next-Generation Microprobe
In the next room, Dr. Wang gives us a glimpse of the next generation of microprobe, the nano-SIMS. It has the benefit of a much smaller beam size and a much larger magnet. The magnet allows it to have an array of seven detectors, so it’s possible to measure seven different masses (isotopes) simultaneously. The larger SIMS machine has only one detector, so if you want to measure different isotopes, you have to measure them in separate sessions by switching the magnet to accommodate the mass of each isotope.

	Dr. Wang explains the operation of the lab’s newer ion microprobe: the nano-SIMS, which is capable of analyzing even smaller samples, including tiny diamonds in meteorites and minute inclusions in gem diamonds. Photo by Duncan Pay/GIA, courtesy of Carnegie Institution of Washington.
The newer instrument’s vacuum chamber is also superior, which is important for measuring light elements like hydrogen. Its two-stage sample chamber allows researchers to achieve higher vacuums and exclude almost all contaminants. The small beam size permits analysis of the tiniest grains in meteorites so researchers can sample the supernova remnants captured in these pre-solar system bodies.

Besides his interest in diamond isotope research, one of Dr. Wang’s other open questions, asked with his DTM colleague Dr. Erik Hauri, centers around water on the moon. Analysis of moon rocks and volcanic glasses in moon rock minerals has shown higher water content than anticipated. Current theories suggest that a Mars-sized planetary body collided with ancient Earth and formed the moon as a result, and that somehow the moon was able to retain water locked up in its rocks and minerals.

Once again, we’re reminded that analysis of nature’s smallest features—tiny inclusions in diamonds, or traces of dust from the early solar system—can lead to groundbreaking discoveries on the scale of our planet’s history, or even larger. We’ll aim to keep in touch with Dr. Wang’s research and update you in the near future. Source: GIA @topic:4


Title: Diamond Quality: A Short History of the 4Cs Abstract: The earliest GIA course materials in the Richard T. Liddicoat Gemological Library and Information Center that mention the 4Cs are from 1949.

	Diamond color, clarity, cut and carat weight are collectively termed the “4Cs” – the factors that, when combined, define a diamond’s quality and ultimately determine its value. Prior to 1940, however, there were no standard terms or factors that defined diamond quality.

	Going back as far as the 1500s, merchants used many different and inconsistent terms to talk about the four elements of a diamond’s value. “Without flaws” or “with imperfections” were used to describe clarity; “tincture” or “tint” to describe color; and terms such as “make well” or “made poorly” to describe cut. “Carat” to describe weight is the only term that was consistently used from the 1500s to today. Because of these different and inconsistent terms, there was no easy way for jewelers to communicate those elements of value to their customers or for their customers to remember them.

	In the early 20th century, Robert M. Shipley, a former retail jeweler, undertook the task of professionalizing the American jewelry industry. To that end, he established GIA in 1931 to provide formal gemological training to aspiring jewelers. Shipley also established the American Gem Society (AGS), a professional guild whose members were GIA graduates.

	Shipley standardized the diamond value terms to color, clarity, cut and carat weight and called them the 4Cs, a mnemonic device to help students and jewelers learn about, remember and explain the factors that determine a diamond’s value.

	Under Shipley’s direction, the term 4Cs became part of industry vernacular through GIA course materials and advertising GIA prepared for AGS-member retailers.

	Teaching Jewelers About the 4Cs

	While it’s not known exactly when Shipley first began to teach the 4Cs at GIA because there are a few gaps in the dates or missing pages from his early course materials, the term appears in newspaper articles in the very early 40s — during the war years — by jewelers who had taken GIA courses. The earliest GIA course material in the archives at the Richard T. Liddicoat Gemological Library and Information Center in Carlsbad that mentions the 4Cs are from 1949. The text reads:

	“These principal properties can be described as the writer [Shipley] first did in preparing advertising for AGS students as Color, Clarity, Cutting and Carat size − the 4Cs of Diamond Value.”

	A GIA student helped produce the first chart used in GIA’s course materials about the 4Cs, “explaining how diamonds can be compared in value by measuring them with these four rulers.” The term also appeared in the AGS booklet “Diamonds” in 1951, and continues to be part of GIA and AGS materials.

	Advertising Spreads the 4Cs Message

	Beginning in 1940, GIA collaborated with De Beers to create advertising designed to stimulate an interest in diamonds. Jewelers began to use the term 4Cs in news articles as early as 1941.

	Later, Shipley arranged to have Gladys Babson-Hannaford, a lecturer for N. W. Ayer & Son (the U.S. advertising firm that represented De Beers), travel around the country to teach jewelers how to talk about the 4Cs to their customers. One of her tours kicked off in 1947 when she advised jewelers to “explain the four factors determining the value of a diamond. We call them the four Cs.”

	N. W. Ayer & Son wrote “Secrets of the Diamond Expert” for The Jewelers’ Circular-Keystone (now JCK magazine) in 1954. It focused on the 4Cs and the material presented seems to have evolved from the talks given in 1947. It was meant as a “speech for jewelers to use to address consumer groups,” according to a secondary headline in the article.

	While De Beers helped with the advertising campaigns that involved the 4Cs, it was not until August of 1962, when the term had become popular, that De Beers adopted the term 4Cs in its national magazine advertising campaign. It stopped using the term purity and started using Shipley’s term clarity (a word starting with ‘c’).

	Today, the 4Cs of Diamond Quality is the universal phrase for referring to the four qualities that determine the value of any diamond, anywhere in the world. This simple mnemonic device, along with the grading standards and practices GIA also developed, means that diamond quality can be communicated in a universal language so diamond purchasers know exactly what they are buying. Source: GIA @topic:4


Title: Is Another 1,000 (or 3,000) Carat Diamond Around the Corner? Abstract: Sotheby’s Hong Kong jewelry director Patty Wong holds a 113 ct D color flawless oval diamond that sold for $30 million in a September 2013 auction. Photo by Russell Shor/GIA

	In the fall of 2015, Lucara’s Kerowe mine in Botswana announced the discovery of the first gem-quality diamond larger than 1,000 carats in more than 110 years. Now, Lucara and others have been doubling down on the search for more mega-stones and believe it’s only a matter of months or a few years – not centuries – until another 1,000-carater turns up.

	Why are they optimistic that such a once-in-a-lifetime find could be repeated so quickly?

	Two reasons: economics and technology. Economics created the necessity and technology created the opportunity. Both have made it possible for the number of very large (over 50 carats polished) diamonds entering the market to increase sharply in recent years and open the possibility of new record-breakers.

	Wealthy Buyers Want Large Diamonds

	On the economic side, the 1990s brought an explosion in wealth around the world, particularly in regions with emerging economies including South Asia, Russia and China, while huge gains in financial markets buoyed wealth in Western economies and the Middle East. This fueled an appetite among the global wealthy for the few mega-diamonds that came up for sale each year.

	Until then, large diamonds often met a violent end after they fell into the mining crushers. There’s no way of knowing how many 100-plus, or even 1,000-carat-plus diamonds may have met that fate. That is because the per-carat price differential between large and commercial-sized [under 10 carats] diamonds was not wide enough that it paid for De Beers – then the dominant diamond producer – to retool its diamond recovery processes to save them.

	It sounds incongruous, but through much of the last century, diamond mining profits came from speed – recovering as many diamonds as possible in the shortest time possible. That meant blasting the kimberlite into small pieces, then using giant steel jaws to crush it into even smaller pieces to quickly separate diamonds from waste rock. De Beers’ executives used to acknowledge that any rough diamond larger than 25 carats stood a good chance of being blown up in the blasting process or crushed into small stones before hitting the recovery plants. The ore conveyors were also run very fast to make processing very efficient, but more difficult to catch large stones before they hit the crusher.

The 603 ct. Lesotho Promise is the largest diamond found at the Letseng mine in Lesotho. London jeweler Laurence Graff and the South African diamond cutting firm Safdico purchased the diamond in 2006 and fashioned 26 D color diamonds of various shapes from the rough, including a necklace valued at $60 million. Photo courtesy of Laurence Graff

	One De Beers executive liked to tell the story of how, at the then-partly owned De Beers Diminico mine in Sierra Leone, a worker noticed a flash coming from near the top of the conveyor that fed the crusher. He hit the emergency stop button, just in time to save a 968.9 ct crystal later known as the Star of Sierra Leone. “Another second and…” he said, clapping his hands together imitating the crusher jaws.

	As the 1990s progressed, however, competition – and prices – for the very few 50 carat-plus diamonds that came up for sale began to intensify as wealthy new buyers entered the market, especially at major auction house sales. One of the key price drivers was the emerging wealth in China and Hong Kong, where both Christies’ and Sotheby’s commenced major jewelry sales, with large diamonds as the cornerstone, before the decade’s end.

	These price increases – nearly four-fold between 1995 and 2005 for polished over 10 carats – reset the economic equation for diamond mining.

The rising price of large diamonds, compared to more commercial sizes, made it possible for operations at the Letšeng mineto become profitable. Photo by Russell Shor/GIA

	Case in point. The Letseng mine in the southern African nation of Lesotho, whose signature production is very large diamonds, though at extremely low grade (about one carat of diamonds for every 100 tons of kimberlite, compared to one carat per ton at other mines, one-tenth that of most diamond operations), was reopened in 2004 after 22 years because increasing prices of such stones made the operation profitable.

	The investment has paid off. The mine has been profitable and claims six of the 25 largest diamonds ever discovered: 478, 493, 527, 550, 601 and 603 carats. In addition, Letšeng recovers about 30 diamonds over 60 carats each year.

	New Technology Saves Large Rough Stones

	The change in economics forced a change in the way mining companies process and recover diamonds. This meant introducing new technologies.

	The first technological advance was in the initial crushing. For many decades, big steel jaws were standard equipment at every diamond mine. They were brutal, but effective in reducing large chunks of kimberlite into manageable smaller pieces. As the new millennium proceeded, miners introduced “kinder, gentler” methods known as “autogenous,” which tumbles or grinds the kimberlite pieces against one another without the intense pressure generated by crushing.

	Such autogenous processes take several forms. Some employ a rotating/oscillating cone in the ore intake chamber that propels the kimberlite pieces into one another and against the sides of the receptacle. After Letšeng employed this system, recovery of 100 carat-plus diamonds more than doubled. Other processes employ large rotating mills that grind the kimberlite pieces against one another.  For more details refer to Letšeng’s Unique Diamond Proposition in the fall 2015 issue of Gems & Gemology.

This is the exterior of the cone oscillator in the processing plant of the Letšeng Mine in Lesotho. The cone method propels the kimberlite pieces into one another and against the sides of the receptacle to reduce the potential for breaking large diamonds. Photo by Russell Shor/GIA

	The second component of new recovery technology is the use of X-ray processing, which replaced or complemented the century-old grease belt system. Diamonds would adhere to grease-coated conveyors and waste rock fell off the sides. The method was fairly effective, but De Beers and others have made a lucrative sideline of re-mining old tailings for diamonds that were overlooked the first time.

	X-ray processing has greatly improved the recovery rate and spared large stones by identifying them before they hit the crushers. XRL (X-ray luminescence) and XRF (X-ray fluorescence) units developed in the 1980s take advantage of the fact that diamonds will fluoresce when exposed to intense X-rays. The crushed kimberlite particles are dropped in a thin stream under a beam of X-rays. When a diamond fluoresces, it activates a photo-detector, triggering a jet of air that deflects the diamond into a collector box.

	Older X-ray recovery units identified diamonds by fluorescence alone, causing non-fluorescent diamonds (which include many large type II stones) and some fancy-color diamonds to slip through to the waste piles. More recent methods adopted at Letšeng and others employ X-ray transmissive (XRT) technology to identify large rough type II crystals trapped in kimberlite and eject them from further processing. The general principle behind XRT sorting is that diamond shows up as a much brighter image than other material; it does not rely upon a diamond’s transparency because it does not deal with visible light range. Even if the sample is sufficiently coated to be completely opaque, the XRT sorter is designed to detect it. It was such a unit that found the 1,109 ct Lesedi la Rona diamond.

	This new technology has enabled smaller mining companies, such as Gem Diamonds, operator of Letšeng, Lucara Diamond Corp. of Vancouver and Lucapa Diamond Co. of Perth, Australia, to recover massive diamonds that, until this decade, had been once-in-a-decade occurrences.

	In addition to the Letšeng, Lucara’s Kerowe mine in Botswana yielded the 1,109 ct Lesedi la Rona diamond, the second largest gem-quality diamond ever found, and an 813 ct diamond and 47 others over 100 carats. Lucapa, which operates the Lulo project in Angola, discovered a 404 ct diamond in February 2016.

The 1,109 ct Lesedi la Rona diamond was the first gem quality rough over 1000 carats found in more than a century.  Mining executives are certain there are others of that size − or larger − awaiting discovery. Photo courtesy of Lucara Diamond Corp.

	Room for Improvement

	The mining companies acknowledge that they still have a way to go. Lucara executives believe a 374 ct diamond found a few days after the Lesedi la Rona diamond had been part of that stone before blasting.

	The largest diamond ever found was the 3,106.75 ct Cullinan from South Africa’s Premier mine two years after it opened in 1903. (That diamond originally weighed an estimated 8,000 carats but was broken by natural forces or blasting.) Premier (now named Cullinan) has been the world’s most prolific treasure house, yielding more than 750 diamonds weighing over 100 carats in its 113-year history.

	After De Beers sold the mine in 2007, the new owners, Petra Diamonds, have been investing in new recovery technology designed to recover diamonds even larger than 3,000 carats.

	The executives of Lucapa and Lucara say they, too, are vying to beat that record. Source: GIA @topic:8


Title: Treated Red and Green HPHT Synthetic Diamonds Abstract: Figure 1. These two treated synthetic diamonds, a 0.57 ct Fancy red and a 0.50 ct Fancy Vivid yellowish green, show strikingly vibrant colors rarely found in natural-color diamonds. Photo by Jian Xin (Jae) Liao.

	Natural-color red and green diamonds are extremely rare and command some of the highest prices in the market. Only a small number of natural diamonds have ever been graded as Fancy red without any modifying hues such as brownish red or orangy red. A 0.57 ct round brilliant with Fancy red color (figure 1, left) was recently submitted to GIA’s New York laboratory for a colored diamond grading report. It showed a heavily saturated and pure red color, without any modifications to the red hue. From another client, we received a 0.50 ct round brilliant graded as Fancy Vivid yellowish green (figure 1, right) for a synthetic colored diamond grading report. The striking features shared by these two specimens caught our attention.

	Examination with a standard gemological microscope revealed that both of them contained pinpoint clouds and metallic inclusions (figure 2), a typical feature of synthetic diamonds grown by high pressure and high temperature (HPHT). Mid-FTIR absorption spectra identified both as type Ib, with the relatively high concentration of isolated nitrogen that is responsible for the yellow to brown color typically observed in HPHT synthetics (Winter 2015 Lab Notes, pp. 430–431).

Figure 2. A large metallic inclusion breaks the table of the Fancy red synthetic diamond. This inclusion and the tiny pinpoint clouds in the background are typical identification features of HPHT synthetics. Photomicrograph by Yixin (Jessie) Zhou; field of view 2.85 mm.

	The strong short-wave UV radiation of the DiamondView (figure 3) showed red and yellowish green fluorescence in the red and green samples, respectively. Furthermore, the presence of both cubic {100} and octahedral {111} growth sectors in the DiamondView images suggested that the specimens formed with a relatively high growth rate that facilitated cubic and octahedral development simultaneously, a strong indicator of synthetic origin (Winter 2015 Lab Notes, pp. 429–430).

	Figure 3. DiamondView fluorescence images of the Fancy Vivid yellowish green synthetic diamond (left) and the Fancy red synthetic diamond (center and right) show similar combinations of cubic and octahedral sectors. Images by Yixin (Jessie) Zhou.

	Diffused lighting showed uneven color zoning in both samples, consisting of their bodycolors and the yellow color from the isolated nitrogen content (figure 4). Spectroscopic analysis revealed that the Fancy red synthetic had an unusually strong peak at 637 nm (NV– center). This peak indicates color alteration by post-growth annealing (T.W. Overton and J.E. Shigley, “A history of diamond treatments,” Spring 2008 G&G, pp. 33–55). In the Fancy Vivid yellowish green synthetic, a concentration of green color on the culet area indicates that artificial irradiation was applied to alter the as-grown yellow color to vivid green. Both synthetic diamonds underwent post-growth treatment to change their color to the desirable red and yellowish green hues. While the yellowish green round brilliant received a synthetic colored diamond report, the undisclosed nature of the Fancy red’s growth required the lab to issue an identification report to properly disclose its synthetic origin.

	Figure 4. Under polarized light, the Fancy Vivid yellowish green synthetic diamond (left) displays patchy yellow color zoning caused by isolated nitrogen and a green color concentration on the culet caused by post-growth artificial irradiation treatment. The Fancy red sample (right) shows yellow to near-colorless zones following the cubic growth sectors, with the red color caused by post-growth annealing. Photomicrographs by Yixin (Jessie) Zhou; fields of view 7.19 mm (left) and 4.79 mm (right). Source: GIA @topic:4


Title: Charting the Increasing Availability and Quality of CVD Synthetic Diamonds Abstract: Welcome to the Fall 2016 Gems & Gemology! This issue brings together synthetic diamonds grown by the chemical vapor deposition (CVD) process, a reversible color modification of zircon, and a rich vein of locality articles including sapphires from Russia, a new Madagascar deposit of the rare gem grandidierite, Vietnamese peridot, and Indonesian cultured pearls.

	Our lead article, by Drs. Sally Eaton-Magaña and James Shigley, reviews the characteristics and key identifying features of CVD synthetic diamonds based on the study of several hundred faceted examples examined by GIA between 2003 and 2016. This comprehensive summary shows how the volume and quality of CVD diamonds changed from what the authors term the “pre-commercial” phase prior to 2008, to the range and color of material available in today’s jewelry marketplace.

		GIA researchers review several hundred CVD synthetics produced between 2003 and 2016.

	Our second paper, by Nathan Renfro, might be of great use to jewelers wishing to restore blue zircons that clients have inadvertently altered to unattractive brown. This “ugly duckling” transformation results from accidental exposure to long-wave ultraviolet radiation from tanning beds or other UV lights. The author explores the nature of this change using spectroscopy to confirm whether exposure to visible light might restore the zircons’ blue color.

	Next, a team of Russian researchers headed by Svetlana Yuryevna Buravleva describes a new deposit of translucent to semitransparent, blue to pinkish blue sapphire crystals and corundum-bearing rocks at Sutara, in the Jewish Autonomous Region of the Russian Far East. The authors postulate that this deposit formed by metasomatism of the contact zone between carbonate rocks and pegmatite veins.

	In our fourth article, lead author Dr. Delphine Bruyère reports on a new occurrence of the rare gem grandidierite in southern Madagascar and provides a gemological characterization of the material, which occurs as bluish green to greenish blue crystals measuring up to 15 centimeters in length. Their analysis confirms that this new locality provides some of the purest grandidierite yet found and will likely be of great interest to museums and collectors.

	In our penultimate paper, Dr. Nguyen Thi Minh Thuyet and colleagues review the gemological and geochemical characteristics of peridot from Vietnam’s Central Highlands, noting similarities with material that originates from xenoliths in alkaline basalts from other localities.

	In our final article, visit a pearl farm in the pristine waters off the Indonesian island of Lombok, where a team of researchers and industry professionals led by GIA’s Nicholas Sturman capture the recovery of bead-cultured and non-bead-cultured pearls from gold-lipped oysters.

	As always, our Lab Notes, Micro-World and Gem News International entries are filled with the latest updates from around the world.

	You can also meet the editors and take advantage of special offers on subscriptions and back issues at the G&G booth in the publicly accessible Galleria section (middle floor) of the Tucson Convention Center during the AGTA show, January 31–February 5, 2017. We would be delighted to see you.

	We hope you enjoy our Fall issue! Source: GIA @topic:4


Title: Cutting Diffraction Gratings to Improve Dispersion (“Fire”) in Diamonds Abstract: A new microlithography process developed to create high-resolution diffraction grating patterns on portions of certain facets can improve the dispersion of light and thus the amount of “fire” in a diamond. These Nanocut plasma-etched diamonds can be identified with magnification by the presence of small, unpolished-appearing areas on the facets where the grating pattern has been created. Round brilliant–cut diamonds displaying such patterns will be classified by the GIA Laboratory as modified round brilliants; as such, they will receive color and clarity grades, but not a cut grade.

	DATA DEPOSITORY

Additional Data
	Winter, 2009 Source: GIA @topic:4


Title: Strongly Colored Pink CVD Lab-Grown Diamonds Abstract: This study characterizes CVD laboratory-grown diamonds from Apollo Diamond Inc. that have strong pink colors produced by high concentrations of NV centers. The samples examined weighed ~0.3–0.7 ct, and their color and clarity grades were comparable to top natural pink diamonds. A combination of optical centers were detected using photoluminescence and absorption spectroscopy. These centers are similar to those seen in previously studied pink-to-red diamonds that have been exposed to HPHT annealing, followed by irradiation and annealing at relatively low temperatures. These pink CVD products can be separated from natural and treated-color natural pink diamonds by a combination of gemological and spectroscopic properties, such as fluorescence color, growth zoning, and absorption features in the infrared and UV-Vis regions.

	Data Depository

Additional Figures
	Submitted by Wuyi WangMay 5, 2010 Source: GIA @topic:4


Title: Analysis of Yellow Diamond Melee for Color Treatment and Synthetics Abstract: Figure 1. These six melee were revealed to be HPHT-treated natural diamonds. Photo by Sood Oil (Judy) Chia.

	Due to the size and quantity of diamond melee in a parcel, gemological analysis is usually not performed on each specimen. As a result, treated and synthetic diamonds are sometimes mixed with natural diamond melee in parcels (Winter 2014 Lab Notes, pp. 293–294).

	Some gemological laboratories are able to properly identify treated and synthetic diamond melee with a combination of infrared absorption spectroscopy, photoluminescence (PL) spectroscopy, and DiamondView fluorescence imaging. GIA’s New York laboratory recently tested two parcels of yellow diamond melee submitted for this screening. The results of their examination highlight the importance of laboratory analysis to correctly establishing the nature and color origin of diamond melee.

	A parcel of six yellow melee (figure 1), each weighing approximately 0.12 ct, was submitted to GIA for testing. Examination confirmed that all six were natural diamonds treated by HPHT (high-pressure, high-temperature) processing. A combination of mid-infrared absorption spectroscopy (4000–400 cm–1) and PL spectroscopy with 633 nm laser excitation was used to detect this HPHT treatment. Spectroscopic analysis in the mid-IR range revealed the presence of isolated single nitrogen impurities. Four stones contained both A- and B-aggregated nitrogen where the B-aggregate was dominant, while the remaining two contained B-aggregated nitrogen; all six contained isolated single nitrogen. PL spectroscopy revealed features that confirmed these were HPHT-treated diamonds.

	Another parcel of 20 yellow diamond melee (figure 2), each weighing between 0.01 and 0.02 ct, was submitted for testing. Mid-IR absorption spectroscopy and DiamondView imaging revealed that three were untreated natural diamonds and one was an HPHT-treated natural diamond; the rest were HPHT synthetics (figure 3). Mid-IR spectroscopy also revealed that 17 of the melee were dominated by A-aggregated nitrogen, three contained both A- and B-aggregated nitrogen, and all 20 contained isolated single nitrogen. The DiamondView images revealed characteristic growth features that helped separate the HPHT synthetic and HPHT-treated material from the natural stones. The HPHT synthetics contained typical cuboctahedral growth patterns, while growth patterns associated with natural diamond formation were observed in the natural diamonds, both untreated and HPHT-treated.

	Figure 2. Of this group of 20 diamond melee, 16 were HPHT synthetics (left). Three were untreated natural diamonds (center), and one was an HPHT-treated natural diamond (right). Photo by Jian Xin (Jae) Liao.

Figure 3. These DiamondView images show characteristic growth features typical of (A) untreated natural, (B) HPHT-treated natural, and (C–F) HPHT synthetic diamond. Images by Manisha Bhoir.

	This analysis highlights the importance of laboratory testing to correctly identifying the nature and color origin of diamond melee, and to minimizing the risk of mixing treated and synthetic diamonds with natural melee in the marketplace. Source: GIA @topic:4


Title: Basel GemFest: Synthetic Diamonds Getting Better, But so is Detection Abstract: Dr. Simon Lawson and Dr. Wuyi Wang discussed synthetic diamonds and detection during the GIA-sponsored GemFest at the Baselworld show. Photo by GIA

                      Experts from GIA and De Beers joined together at the March 2015 Baselworld exhibition to assure a concerned diamond and jewelry industry that the means exist to detect and identify all synthetic diamonds, even those as small as .01 carats (ct.). During the GIA-sponsored GemFest, they also detailed research efforts that will enable labs to continue identifying such stones in the future.

Dr. Simon Lawson, head of technologies UK for De Beers’ research, and Dr. Wuyi Wang, director of research and development for GIA, discussed the two major types of synthetic diamonds in the market and the technologies used to identify them. They also described devices such as GIA DiamondCheck and De Beers’ Automated Melee Screening (AMS) device, DiamondSure and DiamondView, which are used to identify potentially synthetic diamonds.

After Lawson detailed how natural diamonds formed more than 60 miles beneath the Earth’s surface 900 million to 3.5 billion years ago, he and Wang described how High Pressure and High Temperature (HPHT) and Chemical Vapor Deposition (CVD) synthetic diamonds are created in laboratories.

HPHT synthetics, which replicate the natural process of diamond formation, were the first synthetics, developed in the 1950s for industrial use. De Beers created its first gem quality synthetic in the 1980s for research.

HPHT synthetic diamonds are grown in a press with a chamber in the middle. A seed is placed at the bottom of the chamber, covered in a metal solvent catalyst. Graphite powder is placed above the metal solvent, and then the mixture is subjected to extreme pressure and temperatures of 1300 to 1500 degrees centigrade – somewhat higher than the heat that forms natural diamonds.

The different growth conditions between nature and the lab cause HPHT synthetics to form differently, mainly cubo-octahedral versus octahedral or dodecahedral in naturals. The process often leaves telltale metallic inclusions in the stone, some of which may cause it to be attracted to a magnet. These inclusions can be identified visually, though a microscope.

Other identifying characteristics include color zoning, particularly around the culet, which is related to the crystal’s growth characteristics, and distinctive greenish fluorescence.

Although observation may provide some indication that a diamond is synthetic, devices such as GIA’s DiamondCheck and De Beers’ DiamondSure and DiamondView use spectroanalysis, photoluminescence analysis and/or phosphorescence analysis to more definitively identify stones that are synthetic.

Lawson noted that the De Beers-developed DiamondView screening device can pinpoint the signatures of HPHT synthetic’s higher temperature growth and differing crystal structure. In addition, because these synthetics were subjected to high heat for several days instead of millions of years, De Beers’ other screening device, DiamondSure can detect differences in how nitrogen impurities are configured within the stone.

Wang added that several new producers are creating higher quality HPHT synthetics, including Fancy blues, colorless and fancy yellow diamonds. The largest fancy color HPHT synthetic GIA has examined to date was larger than 4 carats. A Russian producer, New Diamond Technology, has produced colorless and near-colorless HPHT synthetics as large as 5 carats, Wang noted, displaying a 5.19 ct.  K color I1 cut-cornered rectangular shape and a 4.30 ct. D color SI1 cushion shape.

The newer synthetic manufacturing process, CVD, has rapidly developed within the last decade. Gasses, usually methane and hydrogen, are heated by microwaves to form a plasma that deposits carbon atoms onto a substrate and crystallizes as diamond. After growth, the synthetic diamonds are sawn into cubes or cylinders.

Unlike HPHT synthetics, CVD stones have no distinctive inclusions, so, like HPHT synthetic diamonds, they can be screened out by use of infrared spectroscopy or the DiamondSure, which can detect their telltale absorption features. Definitive identification may then be made by the DiamondView, which reveals CVD diamonds’ distinctive fluorescence patterns. It was also noted that while annealing (high temperature heat treatment) of CVD can remove some characteristic spectroscopic emission lines, a silicon related impurity that is very common in currently available CVD stones  (and very rarely found in natural diamonds) is extremely difficult to remove.

Because CVD synthetics grow differently from natural diamonds, they show a distinctive striation pattern under magnification and have a distinct orange fluorescence. This color usually changes to green for diamonds that are annealed (heated at very high temperatures) after growth.

Wang pointed out that, while today’s market is still dominated by natural diamonds, the number of synthetics is increasing and their quality continues to improve, making disclosure necessary. Gem labs, he said, play a critical role in that disclosure.

As an example, he showed CVD synthetic diamonds, ranging from 0.10 to 0.30 carats, produced in 2003 that had a distinctive brown color. Within three years, producers learned to develop near colorless stones, and by 2011, they could obtain near-one-carat weight and near colorless products. Today, some near-colorless CVD’s are as large as 3 carats.

Wang also described how CVD producers can create fancy colored diamonds by controlling the levels of nitrogen in the growing process. He showed several examples of lab-grown brownish pink and pink diamonds. He also pointed out that CVD’s from different producers have distinct identification features of their own.

Lawson noted that De Beers continually refines its DiamondSure and DiamondView to improve detection capabilities, particularly as synthetic production methods change. The AMS, an automated version of DiamondSure, has been released to enable more economic testing of melee stones down to .01 ct.

Wang said the challenges to identify diamond synthetics can be significant, especially when they are mixed into parcels of melee. He displayed an image of a pendant with 104 very small fancy yellow diamonds, one of which was a synthetic weighing .004 carats.

He said GIA’s screening device, GIA DiamondCheck, can flag all potentially synthetic or treated diamond and non-diamond imitations from .01 to 10 carats. DiamondCheck employs spectroscopic analysis to provide rapid screening for colorless and yellow diamonds. The device can effectively screen pink diamonds as well, provided they are boiled in acid first to remove any possible coatings.  DiamondCheck also identifies HPHT treated natural diamonds, and non-diamond simulants.

DiamondCheck,  DiamondSure and AMS are rapid screening devices that flag potentially synthetic diamonds. The DiamondView presents more detailed spectral analyses that require review by a trained technician to determine if the diamonds are natural or synthetic.

Both researchers stressed the challenges posed by the continued improvement of synthetic diamonds in size, quality and ability to appear more natural. GIA scientists, more than 40 on staff, have been researching synthetic diamonds since the first gem quality specimens were created in 1971. They also stressed confidence that De Beers and GIA will be able to keep pace with these developments and be able to identify them accurately.

“Our research not only deepens the world’s understanding of gems, but protects those who buy or sell them,” Wang concluded.

	Dr. Simon Lawson, head of technologies for De Beers’ research, explained how natural diamonds form and how synthetic diamonds are created using the HPHT and CVD processes. Photo by GIA Source: GIA @topic:4


Title: Record Prices and Low Profits: The Bifurcated Diamond Trade Abstract: The Pink Star, a GIA-graded 59.60 carat Fancy Vivid pink diamond, sold for $83.2 million at a Sotheby’s auction Nov. 12, 2013 in Geneva. Photo courtesy of Sotheby’s. Update: According to media reports, Sotheby’s cancelled the sale of the Pink Star several months after the auction when the winning bidder was unable to complete the transaction.

	Two rare fancy colored diamonds set landmark price records last week at Geneva auctions. In the meantime, the more mundane side of the world diamond industry is still struggling with reductions in financing, tight liquidity and soft polished prices.

First the auctions: Christie’s sold a GIA-graded 14.82 carat Fancy Vivid orange diamond for $35.5 million.  At $2.4 million per carat, this is the highest-ever per-carat price for a gemstone at auction. The following day, a bidder paid $83.2 million ‒ the highest price ever paid for any gemstone anywhere ‒ for the 59.6 carat Pink Star, a Fancy Vivid pink diamond at Sotheby’s. This GIA-graded pink didn’t just beat the old record of $46 million (also a pink diamond), it demolished it. (Update: According to media reports, Sotheby’s cancelled the sale of the Pink Star several months after the auction when the winning bidder was unable to complete the transaction.)

	The Orange, a GIA-graded 14.82 carat Fancy Vivid orange diamond, sold for $35.5 million at a Christie’s auction Nov.11, 2013 in Geneva. Photo courtesy of Denis Hayoun Diode SA Geneva

	These were the top lots. Buyers, largely anonymous, also paid top prices for other lots: $4.6 million for the Cote D’Azure brooch containing a 58.29 carat Burmese sapphire and nearly $10 million for the Patino emerald and diamond necklace. The Pink Star helped Sotheby’s auction total set a new total record for a jewelry sale ‒ more than $199 million ‒ while Christie’s was $125 million.

	And, to provide context, there were also record prices in the auction houses’ fine art sales last week. A work by the Irish-born British artist Francis Bacon drew a top bid of $142 million ‒ the most money ever paid for a piece of art at auction. In the past two years, five paintings have changed hands at auction for more than $100 million each and a Cezanne reportedly sold for more than $250 million in a private sale.

	Luxury analysts say the market for such top pieces is driven by the ultra-wealthy in Western countries who are still concerned about uncertain financial markets and low interest rates. They view rare gems and art as a more certain investment, while, in other parts of the world, buyers use such assets as a hedge against political uncertainty.

Other Diamond News: Little of this translates to the market for diamonds and gemstones that sell for thousands (and hundreds) of dollars, instead of millions.

	Lack of profits and liquidity issues dominated the inaugural De Beers sight held in Botswana, November 12-15. The size of the sight was reportedly $470 million, though some companies may have received additional allocations. According to one report, prices were moderated slightly, about 2% on some goods, and the assortments were more closely in line with market needs.

	Despite this, some dealers did ‒ again ‒ leave goods on table they could not cut or resell profitably, though apparently not at the levels of the previous sights.

	The sight coincided with the first full tender auction of Botswana-mined rough by the Okavango Diamond Company, the auction subsidiary created by De Beers and the Botswana government to boost local manufacturers. Unlike the pilot sale where prices of some rough categories ran substantially higher than comparable sight goods, these results were reportedly in close alignment with De Beers set-sale prices. The banks’ sharp credit reductions of the past two months kept the bidding down at the tender sale.

	On an encouraging note, holiday jewelry sales in the U.S. are expected to increase about 4-5% over the 2012 total, according to most estimates. In unit terms, this increase should be a point or two higher because of the decline in gold and (to a much lesser extent) diamond prices during the year.

	For diamonds, retailer reports continue to head in diverging directions. Mid-priced stores and chains look to down-trade quality and size (lots of calls for “light sizes” have been reported), while higher-end retailers are in search of top makes.

	Indeed, one luxury market study reports that the Americas have surpassed China in terms of overall luxury goods spending, registering a 4% increase in 2013 compared with 2012, versus a 2.5% increase in China.

	A steady pace of store openings in second-tier cities in the U.S. has helped drive growth in the region, according to the 2013 Luxury Goods Worldwide Market study. This trend, along with an increasing number of Chinese tourists in Las Vegas and Los Angeles, has boosted growth. The report was commissioned by Altagamma, the Italian luxury goods manufacturers’ industry foundation. Source: GIA @topic:8


Title: Book Review: Collector’s Guide to Herkimer Diamonds Abstract: By Michael R. Walter, softcover, 96 pp., illus., publ. by Schiffer Publishing, Ltd. Atglen, PA, 2014, US$19.99.

	Quartz, chemically the simplest form of the silicates, is abundant in the earth’s crust. Herkimer diamonds are a unique form of quartz crystal found in the state of New York. Most of the brilliant, water-clear crystals show the classic 18-sided, doubly terminated hexagonal form.

	Author Michael Walter gives us an in-depth look at every aspect of Herkimer diamonds. Mineralogical properties such as crystal shapes, sizes, surface growth features, and crystal combinations are fully described. Calcite, dolomite, iron sulfides, and hydrocarbons are associated minerals. Inclusions that provide clues to the origins of the Herkimer diamonds are solids, liquids (salt water or petroleum), gases (most often carbon dioxide), two- and three-phase inclusions, and negative crystals. Anthraxolite, formed by polymerization of petroleum over geological time periods, is the most common solid inclusion.

	The geological history of Herkimer diamonds is an intriguing one that begins at the bottom of a shallow sea about 495 million years ago. The material that would later form the crystals was deposited as a waxy organic material along with quartz sand and masses of pyrite. All of this was encased in a rock made up of two carbonate minerals: dolomite and calcite. Sediments slowly buried the rock and its temperature rose. As a result, molecules that had been holding quartz dissolved from the sand in solution were broken apart by thermal splitting. This caused the quartz to come out of solution very slowly and resulted in the growth of quartz crystals of exceptional clarity.

	The book’s main purpose is about where to go for treasure hunting and how to work the rock based on firsthand experience. No single aspect of field collecting goes undiscussed. Collecting is only possible during the favorable weather of summer. The rock is hard, and the author gives invaluable information on equipment and tools and how to use them. Specific methods used to effectively extract Herkimer diamonds are described.

	A full chapter is dedicated to the preparation of specimens: cleaning, trimming and preservation. Some of the mines are operated as fee locations and open to the general public. These and some closed mines and locations outside the traditional Herkimer diamond region are documented. A handy appendix section contains maps and GPS coordinates of Herkimer diamond localities, including Ace of Diamonds, Herkimer Diamond Mines, Crystal Grove Mine, Diamond Acres, and Hickory Hill.

	Good rock and mineral collecting field guides are hard to find. This guide offers 210 vivid color images and a well-written, easy-to-read text. This book is a must have if you are thinking of prospecting for Herkimer diamonds. Source: GIA @topic:7


Title: Treated Pink Diamond with HPHT Synthetic Growth Structure Abstract: Figure 1. This multi-step treated 1.62 ct Fancy pink natural diamond shows what appears to be HPHT synthetic growth structure. Photo by Sood Oil (Judy) Chia.

	HPHT synthetic diamonds are grown using high pressure and high temperature but with a much higher growth rate than natural diamond. Consequently, their growth structures are different. GIA’s New York lab recently examined a multi-step treated diamond with a growth structure similar to that of HPHT synthetics. The 1.62 ct Fancy pink type IIa round brilliant seen in figure 1 showed spectral characteristics suggestive of HPHT treatment, irradiation, and annealing. This diamond was internally clean, except for the presence of strong, colorless internal graining (figure 2). Tatami and banded strains with strong interference colors could be seen under cross-polarized light (again, see figure 2). Based on these microscopic features, we concluded that this was a natural diamond.

Figure 2. Tatami strain (left, field of view 3.20 mm), banded strain (middle, field of view 3.20 mm), and heavy internal graining (right, field of view 2.45 mm) are evidence of a natural diamond.  Photo by Kyaw Soe Moe.

	DiamondView imaging of the stone showed cuboctahedral growth with dark sectors and pink coloration (figure 3). This crystal habit is usually observed in HPHT-grown synthetic diamonds. As seen in figure 3 (left), the cubic {100} sector can be located in the pavilion, along with octahedral {111} sectors. In order to understand more about this growth, we compared it with a type IIa 0.27 ct HPHT synthetic, which was treated post-growth to induce a Fancy Intense orangy pink color (figure 3, right). Both specimens showed similar fluorescence patterns; however, the natural diamond’s greenish blue phosphorescence was evenly distributed, as seen in the middle image of figure 3. This is unlike the dark images yielded from type IIa pink HPHT synthetics, which are not phosphorescent.

Figure 3. DiamondView fluorescence images of the treated 1.62 ct pink natural (left) and the post-growth treated 0.27 ct pink HPHT synthetic (right) showed similar growth patterns, containing cubic {100} sector and octahedral {111} sectors. The middle image of phosphorescence of the 1.62 ct pink natural diamond showed even color distribution without growth sectors. Type IIa pink HPHT synthetic diamonds are usually not phosphorescent. Images by Kyaw Soe Moe.

	Although most natural diamonds show octahedral growth structure in DiamondView images, some natural gem-quality colorless and yellow diamonds may show cuboctahedral growth (Winter 2010 Lab Notes, pp. 298–299; Winter 2011 Lab Notes, p. 310; Spring 2013 Lab Notes  pp. 45–46). Some non-gem-quality diamonds possess cuboctahedral form (D.G. Pearson et al., “Orogenic ultramafic rocks of UHP (diamond facies) origin,” in R.G. Coleman and X. Wang, Eds., Ultrahigh Pressure Metamorphism, Cambridge University Press, 1995, pp. 456–510). Growth rate, pressure, and temperature of geological environment control the habit of a diamond crystal. A slow growth rate causes octahedral crystal growth, but a high growth rate can facilitate cubic {100} and octahedral {111} sectors developing simultaneously. As a result, cuboctahedral habit can be formed naturally.

	While the DiamondView is very reliable at revealing the growth structure of natural vs. synthetic diamond, it is important to correctly interpret all identifying characteristics. When cuboctahedral growth structure is observed, one should look for other features to support the origin. Microscopic features and spectral characteristics are useful for this purpose. Source: GIA @topic:4