Publish Year: 2018 Title: Suggested Reading on Diamond Inclusions Abstract: Breeding C.M., Eaton-Magaña S., Shigley J.E. (2018) Natural-color green diamonds: A beautiful conundrum. G&G, Vol. 54, No. 1, pp. 2–27, http://dx.doi.org/10.5741/GEMS.54.1.2
Eaton-Magaña S., Breeding C.M. (2018) Features of synthetic diamonds. G&G, Vol. 54, No. 2, pp. 202–204, http://dx.doi.org/10.5741/GEMS.54.2.202
Eaton-Magaña S., Breeding C.M., Shigley J.E. (2018) Natural-color blue, gray and violet diamonds: Allure of the deep. G&G, Vol. 54, No. 2, pp. 112–131, http://dx.doi.org/10.5741/GEMS.54.2.112
Eaton-Magaña S., Shigley J.E., Breeding C.M. (2017) Observations on HPHT-grown synthetic diamonds: A review. G&G, Vol. 53, No. 3, pp. 262–284, http://dx.doi.org/10.5741/GEMS.53.3.262
Koivula J.I. (2000) The MicroWorld of Diamonds. Gemworld International, Northbrook, IL, Inc., 157 pp.
Shirey S.B., Shigley J.E. (2013) Recent advances in the understanding the geology of diamonds. G&G, Vol. 49, No. 4, pp. 199–222, http://dx.doi.org/10.5741/GEMS.49.4.199
Smit K.V., Myagkaya E., Persaud S., Wang W. (2018) Black diamonds from Marange (Zimbabwe): A result of natural irradiation and graphite inclusions. G&G, Vol. 54, No. 2, pp. 132–148, http://dx.doi.org/10.5741/GEMS.54.2.132
Smith E.M., Shirey S.B., Nestola F., Bullock E.S., Wang J.H., Richardson S.H., Wang W. (2016) Large gem diamonds from metallic liquid in Earth’s deep mantle. Science, Vol. 354, No. 6318, pp. 1403–1405.
Smith E.M., Shirey S.B., Richardson S.H., Nestola F., Bullock E.S., Wang J.H., Wang W. (2018) Blue boron-bearing diamonds from the Earth’s lower mantle. Nature, Vol. 560, No. 7716, pp. 84–87.
Smith E.M., Shirey S.B., Wang W. (2017) The very deep origin of the world’s biggest diamonds. G&G, Vol. 53, No. 4, pp. 388–403, http://dx.doi.org/10.5741/GEMS.53.4.388 @topic:10


Publish Year: 2016 Title: Coesite Inclusions with Filaments in Diamond Abstract: Figure 1. Left: A Vivid yellow 0.164 ct diamond containing coesite inclusions. The diamond is 3.52 mm in diameter. Center: Photomicrograph of a dense region of coesite inclusions with filaments; field of view 1.26 mm. Right: A photomicrograph of a single coesite inclusion, with filament gradually going out of focus to the right; field of view 100 μm. Photomicrographs by Jian Xin (Jae) Liao (left) and Evan M. Smith (center and right).
GIA’s New York lab recently encountered an HPHT-treated Fancy Vivid yellow diamond with unique inclusions. The diamond was determined to be HPHT-treated due to the presence of a strong solitary peak at 1344 cm–1 in the infrared absorption spectrum, indicating isolated nitrogen C-centers, a relatively even distribution of color, and the absence of certain peaks in the diamond’s Raman spectrum. However, the color treatment of this diamond was not its most interesting aspect. The diamond was unique for possessing many small inclusions with fine, tail-like filaments (figure 1). Visually, the filaments within this 0.164 ct round brilliant-cut diamond resembled horsetail inclusions in demantoid garnet. Raman spectroscopy of four separate inclusions gave peaks for coesite, a high-pressure SiO2 polymorph (figure 2).

Figure 2. Raman spectra of four inclusions corresponding to coesite with high remnant
pressure inside each inclusion. Spectra have been vertically offset for clarity.
The measured peaks of coesite are shifted with respect to reference spectra due to high confining pressures within each inclusion. The shift of the main peak from its unconstrained position at 521 cm–1 to the measured peak in the inclusions, at 533 ± 1 cm–1, can be used to calculate the internal pressure, which is an incredible 4.3 ± 0.4 GPa (R.J. Hemley, “Pressure dependence of Raman spectra of SiO2 polymorphs: α-quartz, coesite, and stishovite,” in M.H. Manghnani and Y. Syono, Eds., High-Pressure Research in Mineral Physics, AGU, Washington, D.C., pp. 347–359). When a diamond is carried to the surface, the diamond and its inclusions do not decompress coherently, so it is fairly common for inclusions to have some amount of “locked-in” remnant pressure. HPHT treatment is unlikely to have modified this remnant pressure, although the possibility cannot be entirely ruled out without more detailed study. These particular coesite inclusions preserve an especially high pressure because the inclusions are small. Larger inclusions are more likely to crack or deform the surrounding diamond and relieve some of the built-up pressure.

Coesite inclusions are not uncommon in diamond, and they are interpreted to indicate an eclogitic mantle host rock paragenesis. The curvilinear filaments extending from the inclusions are, however, both uncommon and unusual. They have a preferred orientation, extending to the right in figure 1 (center). This direction corresponds with the interpreted direction of growth, outward from the center of the diamond. Most filaments are singular, measuring 20–200 µm long, but a few branch into a fan-like spray of sub-parallel filaments. The thickness of each filament is less than 1 µm, making it difficult to observe or characterize them in more detail. Interestingly, the inclusions occur within discrete regions in the diamond, which correspond to cuboid {100} growth sectors when examined in the DiamondView (short-wave UV fluorescence imaging). A possible explanation for the filaments is that they are grown-in dislocations, originating from the point where the diamond just finished enveloping each inclusion. The filaments resemble the dislocations seen in X-ray topography of natural diamonds (e.g., B. Rondeau et al., “On the growth of natural octahedral diamond upon a fibrous core,” Journal of Crystal Growth, Vol. 304, 2007, pp. 287–293). A dislocation alone, however, would not be optically visible. Small amounts of solid or fluid material trapped with the dislocation might be responsible for its visibility. @topic:4


Publish Year: 2014 Title: Mixed-Type Cape Diamond Abstract: Figure 1. This 2.16 ct Fancy orangy yellow diamond is a mixed-type IaA>B. Photo by Jian Xin (Jae) Liao.

Natural yellow type Ia or “cape” diamonds, the most common of all colored diamonds, are identified by the N3 (415 nm) and N2 (478 nm) absorption lines in the UV-visible range. These defects produce the characteristic yellow hue, and the N3 line produces the blue luminescence, so often observed in these stones. Weaker bands at 452 and 465 nm may also be visible (C.M. Breeding and J.E. Shigley, “The ‘type’ classification system of diamonds and its importance in gemology,” Summer 2009 G&G, pp. 96–111).

The New York laboratory recently examined a 2.16 ct Fancy orangy yellow diamond (figure 1) with unusual features for a cape stone. When analyzed with a UV-Vis spectrometer, it exhibited a cape spectrum and an unexpected 480 nm band, a defect usually associated with orange color (figure 2). Infrared spectrometry revealed a well-defined IaAB diamond, as opposed to the saturated Ia spectrum typically associated with cape diamonds. These abnormal features prompted further testing, and the DiamondView revealed zoned blue and yellow fluorescence (figure 3). Raman spectroscopy of the transparent, elongated crystal within the diamond, visible in the DiamondView, identified it as a colorless garnet, a common inclusion in cape diamonds.

Figure 2. UV-visible spectrum displaying “mixed” cape (red) with overlay of “normal” cape (blue).

Figure 3. The cape diamond’s DiamondView image displays blue and yellow fluorescence, along with an elongated crystal. Image by Paul Johnson.
While the specific structure of the 480 nm optical defect is not yet understood, it is known to be associated with yellow fluorescence (Y. Luo and C.M. Breeding, “Fluorescence produced by optical defects in diamond: Measurement, characterization, and challenges,” Summer 2013 G&G, pp. 82–97). The defect is also sometimes attributed to substitutional oxygen in type I diamonds. From our data and test results showing no evidence of laboratory-produced alteration, we can conclude that this stone is a natural and very rare example of a cape diamond mixed with a 480 nm band causing the orange component. @topic:4


Publish Year: 2014 Title: Xenotime Inclusion in Yellow Diamond Abstract: Diamond inclusions can be analyzed using Raman spectroscopy, ideally when they are close to or breaking the surface. The New York lab recently had the opportunity to study a rare inclusion of xenotime protruding from the surface of a 0.55 ct Fancy Intense yellow diamond (figure 1).

Figure 1. This 0.55 ct yellow diamond contained a rare mineral inclusion of xenotime. Photo by Kyaw Soe Moe.
The yellowish brown inclusion was located in the pavilion near the girdle; radiation stains were observed at the contact area with the host diamond (figure 2, inset). Radiation stains and the nature of the surface penetration suggested that it formed inside an etch channel as an epigenetic inclusion. Raman spectroscopy showed peaks consistent with xenotime at 1012.8, 1064.5, 1117.5, 1158.4, and 1246.6 cm–1 as seen in the figure 2 spectrum.

Figure 2. The xenotime inclusion broke through the pavilion surface (inset; magnified 80×). Radiation stains were also observed at the contact with the host diamond (see arrow). The Raman spectrum, using a 514 nm laser, shows xenotime peaks at 1012.8, 1064.5, 1117.5, 1158.4, and 1246.6 cm–1. Photomicrograph by Kyaw Soe Moe.
Minerals that formed outside of the diamond stability field can be found inside a diamond (see Spring 2009 Lab Notes, pp. 54–55). Xenotime (yttrium orthophosphate, YPO4) occurs mainly in granitic pegmatite and also in metamorphic rocks such as biotite gneiss (E.J. Young and P.K. Sims, Petrography and Origin of Xenotime and Monazite Concentrations, Central City District, Colorado, Geological Survey Bulletin 1032-F, 1961, pp. 273–297). Young and Sims proposed that granitic fluids such as granodiorite mobilized rare earth elements (REE) and phosphates from biotite gneiss in Colorado. Later, these ions crystallized to form unusually high concentrations of xenotime and monazite in migmatized parts of gneiss. The granitic fluids may have percolated within diamond deposits in continental crust, and REE ions could have been deposited and crystallized inside etch channels, as observed in this yellow diamond. Radiation stains associated with xenotime, which is one of the few naturally occurring yttrium minerals, may contain trace amounts of uranium and be slightly radioactive.

Associations of xenotime with diamond have been previously reported. E. Hussak described intergrowths of monazite and xenotime in diamond-bearing sands in Brazil (“Mineralogische Notizen aus Brasilien,” Tschermaks Mineralogische und Petrographische Mitteilungen, Vol. 18, 1899, p. 346). More recently, xenotime inclusions have been reported in carbonado from the Macaubas River in Minas Gerais (M. De Souza Martins, Geologia dos Diamantes e Carbonados Aluvionares da Bacia do Rio Macaubas (MG), Ph.D. thesis, Universidade Federal de Minas Gerais, Instituto de Geociencias, Belo Horizonte, Brazil, 2006). To the best of our knowledge, xenotime inclusions in gem-quality diamond have never been reported. @topic:4


Publish Year: - Title: Famous Diamonds Examined by GIA Abstract: The Hope diamond, the Dresden Green, the Idol’s Eye, the Portuguese Diamond and the Moussaieff Red – these famous diamonds are spectacularly beautiful jewels that have been admired for centuries. An aura of mystery has always surrounded these rare natural wonders, so it was quite an honor when GIA researchers examined them.

View Gallery

The Hope diamond
VS1 • 45.52 ct

The Hope diamond. Courtesy of Chip Clark/Smithsonian Institution.
The Hope diamond may be the most famous colored diamond in the world. A team of GIA gemologists graded it in 1988. Because they were able to weigh the diamond unmounted, they quickly made a notable discovery: the diamond was 45.52 ct, and not 44.50 ct, which had been its previously recorded weight. GIA graders also reported that the Hope diamond is a cushion brilliant cut. The diamond was color graded as a natural color Fancy dark grayish blue diamond.

Since the 1800s, the Hope diamond had been described as being flawless. During their examination, the GIA team noticed that the diamond had accumulated a few wear marks over the years and had whitish graining and a few minor feathers. Its clarity was graded as VS1 (Very slightly included). Good polish and Fair to Good symmetry were also noted. Technical specifications aside, the Hope diamond captivates the imagination like no other gemstone.

The Dresden Green
41 ct

The Dresden Green
In late 1988, GIA gemologists secured permission to examine the famed Dresden Green diamond in the Green Vaults, which was then in East Germany. They were particularly excited, as it promised to provide insight into distinguishing natural from laboratory-irradiated green diamonds (radiation is usually the cause of color in both instances). Because the diamond’s history had been recorded since 1741, researchers could be confident that it had not been treated in a laboratory. As the diamond remained mounted upon examination, GIA gemologists were not able to issue a grading report.

GIA researchers described the Dresden Green as Fancy green, with a modified pear-shaped brilliant cut. The natural green color has medium tone and slightly grayish saturation. The Green Vaults records indicate it weighs 41 ct.

The Portuguese Diamond
VS1 • 127.01 ct

The Portuguese Diamond. Courtesy of Harold and Erica Van Pelt.
Of South African origin, the Portuguese Diamond weighs 127.01 ct. GIA gemologists graded it an M on the GIA Color Scale, and gave it a VS1 clarity grade because of a small bruise on one of the facets and two very minor scratches on the table.

The Portuguese has Very Strong blue fluorescence, and this may help mask the faint yellow color in the diamond. Because the fluorescence is so strong, in 1924 it was advertised by Black, Starr & Frost to be a blue diamond.

Idol’s Eye
VVS1 • 70.20 ct

Idol’s Eye. Courtesy of Graff Diamonds.
Another famous diamond shrouded in myth, the Idol’s Eye was probably mined in India’s Golconda District – an area famed for producing fine diamonds. There are many tall tales about the diamond, including one that says the Idol’s Eye is also the Nassak. This has been disproven. The first confirmed documentation of the Idol’s Eye was in one of the lots being sold at auction by Christie’s London in July 1865.

GIA gemologists confirmed that the Idol’s Eye weighs 70.20 ct. Its color grade is Very Light blue and its clarity is VVS1 (Very very slightly included).

The Moussaieff Red
5.11 ct

The Moussaieff Red
Although the Moussaieff Red weighs just 5.11 ct, it’s a predominantly red diamond (no secondary hues like purple), which means it’s incredibly rare. A description of Fancy red is remarkable. GIA records show that from 1957 to 1987 there was no mention of a GIA report issued for a diamond with “red” as the only descriptive term.

Only a handful of Fancy red diamonds are known, because in diamonds the color red is often modified with another hue, such as purplish red or orangy red.

A Brazilian farmer discovered the Moussaieff Red in the 1990s. It was cut and polished from a 13.9 ct crystal. @topic:10


Publish Year: 2018 Title: Fourth International Diamond School Abstract: Figure 1. During the Fourth International Diamond School, Pierre Cartigny delivers a presentation on stable isotopes with support from organizer Fabrizio Nestola. Photo by Marco Cuman.

At the end of January 2018, some 92 attendees and 18 teachers gathered once again in the picturesque northern Italian town of Brixen-Bressanone for the fourth International Diamond School (IDS), themed “Diamonds: Geology, Gemology, and Exploration.”

As in previous years, the school was underwritten by the Gemological Institute of America (GIA) in addition to the Deep Carbon Observatory (DCO), the Society of Italian Mineralogical (SIMP), and the University of Padua. Professor Fabrizio Nestola (University of Padua) served as local organizer extraordinaire and was assisted on the organizing committee by four of the presenters: Matteo Alvaro, Graham Pearson, Steven Shirey, and Wuyi Wang.

The academic activities took place in a well-appointed auditorium owned by the University of Padua, while meals and social activities were held in the sixteenth-century Hotel Elephant—so named because the original building saw the arrival of an elephant from Ceylon—a gift to the Austrian royal family that caused a sensation and inspired artists and poets.

For the first three days, the school provided a general overview of the recent advances in diamond research, focusing specifically on the geology, exploration, and gemology of diamond from leading scientists in their fields. A brief summary of their talks follows.

Jeffrey Harris (University of Glasgow, UK) gave a very interesting overview of the history of gem diamonds from the sixth century (AD) onward. The modern era, leading directly to today’s active mines, began in the 1870s in South Africa with the discovery of rich placer deposits. This period was followed by recognition of kimberlite as the diamond host rock and the battle between Barnato and Rhodes for supremacy over the kimberlite pipes in the Kimberly area.

John Armstrong (Karowe Mine, Lucara Diamond, Botswana) is the world’s expert on how to extract (and not break!) very large diamonds. He outlined automated methods such as X-ray transmission to detect low-nitrogen stones and crushing methods that use the host kimberlite itself to minimize breakage.

Herman Grütter and Jennifer Pell (Peregrine Diamonds, Vancouver) spoke via Skype about microdiamond size frequency distributions (SFDs) and their practical use in macrograde forecasting to predict whether it will be economically worthwhile to mine a kimberlite. Each large sample of diamondiferous kimberlite dissolved by caustic fusion has its own microdiamond distribution in a plot of diamond grade (diamonds per ton) versus diamond size (carat weight). This negative correlation can be shown to merge with the same macrodiamond distribution for mines, which becomes the basis for the forecast. The challenge is that not all localities follow this relationship.

In a second Skype talk, Grütter spoke about pyroxene thermobarometry and a xenocryst-based approach. Using single clinopyroxenes from concentrates and indicator minerals, exploration major tectonothermal events in the mantle lithosphere are revealed. Because it takes some 800 million years for the lithosphere to equilibrate thermally, large clinopyroxene data sets can reveal heretofore unknown C-O-H flux fronts and mantle plumes.

Bruce Kjarsgaard (Geological Survey of Canada) discussed experimental constraints on kimberlite origin, ascent, and eruption. His talk focused on kimberlite mineralogy and isotopic compositions for kimberlite origin and experimental petrology for ascent and eruption. One of the basic questions still unanswered is whether kimberlite magmas are initially carbonatitic melts or some form of transitional melt.

Nikolay Sobolev (V.S. Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russia) spoke about inclusions in Siberian diamonds and their polycrystalline aggregates and specific features of orogenic diamonds from Kazakhstan. His talk offered a useful review of inclusion types.

Making and stabilizing the deep diamond-bearing roots of the continents was the subject of a cutting-edge review by D. Graham Pearson (University of Alberta, Canada). Rheology turns out to be more important than buoyancy in preserving continental roots, and this stiffness makes them essentially plume-erosion proof. Lateral compression serves as a means to accumulate residues of any origin and form thick depleted lithosphere of more depleted composition. The process also accounts for late Archean intra-crustal differentiation. A good modern analog to Archean craton formation may be seen in the new continent of Zealandia.

Thomas Stachel (University of Alberta) covered the entire subject of diamond formation in the earth’s mantle. The newest thinking on diamond formation places less emphasis on solid-solid reactions or host-rock buffering and more emphasis on the diamond-forming fluids themselves. Critical factors include temperature change, reduction of CO2, and presence of organic species including methane.

Oded Navon (The Hebrew University of Jerusalem) addressed diamond-forming fluids. He made the important points that there is a huge diversity of diamond-forming fluids by major and trace element composition and that the gem fluids are little different from those for fibrous diamonds.

Steven Shirey provided a framework with which to categorize diamond ages that can be used to establish meaningful age uncertainties with his talk. Since diamond ages rely on mineral inclusions for dating, debate over the years has been focused on whether these inclusions are protogenetic (existing before encapsulation) or syngenetic (simultaneous growth of the diamond and the inclusion). It is clear that many inclusions are mineralogically protogenetic while being geologically syngenetic.

Matteo Alvaro (University of Pavia, Italy) detailed new approaches to in-situ crystallographic study of mineral inclusions in diamond. Interestingly, mechanical re-orientation is a feature of the encapsulation of many silicate inclusions.

Pierre Cartigny (Institut de Physique du Globe de Paris; figure 1) discussed stable isotopes and diamonds in a talk that argued for massive carbon recycling into the mantle and considered the fractionation effects that occur between C, N, and the various kinds of fluids and sources from which well-studied diamond suites have come.

Diamond gemology and advanced technologies to replace visual observations were discussed by Wuyi Wang (GIA, New York). The talk covered GIA’s research role in the $80 billion diamond trade and its assessment of color, cut, clarity, and carat weight. Dr. Wang also discussed GIA’s internships and fellowships for research scientists.

Christopher M. Breeding (GIA, Carlsbad, California) covered the ever growing field of diamond defects and the identification of color treatment. While sophisticated analytical techniques allow GIA to associate color and treatment with lattice-scale mechanisms in diamond, each color requires considerable research analysis to pin down its defect mechanism.

Ulrika D’Haenens-Johansson (GIA, New York) addressed the synthesis of manmade gem diamonds and their detection. Diamonds grown by the two main methods—high-pressure, high-temperature (HPHT) growth and chemical vapor deposition (CVD)—currently can be detected chiefly from their isotopic composition and the N content of their starting compounds.

In her review of advances in in-situ isotope measurement in diamond and their inclusions, Emilie Thomassot (CNRS, Nancy, France) went over many of the theoretical and practical considerations affecting the accuracy and precision of ion microprobe measurements for stable isotopes, especially sulfur.

Steven Reddy (Western Australian School of Mines at Curtin University) described an exciting new direction in his talk on atom probe microscopy and its potential applications to diamond research. With this instrument, the analytical specimen is prepared in the shape of a needle and atoms from it are directed into a time-of-flight (TOF) mass spectrometer. One can retrieve the exact position of the atoms in the structure and even measure their isotopic composition. The potential is there to look at very tiny inclusions in diamond in this manner.

Dan Howell (University of Padua, Italy) covered the major uncertainties of Fourier-transform infrared (FTIR) studies of diamonds and how to overcome them. This basic technique, applicable nondestructively to any diamond, remains one of the most important ways to characterize specific diamonds and their integrated thermal history.

Figure 2. International Diamond School attendees discuss recent research. Photo by Marco Cuman.
Following the tradition of previous years, the International Diamond School went beyond these formal lectures (figure 2) to include practical sessions focused on microscopic observations of a complete inclusion-bearing diamond collection on the fourth day. The collection was made available to the IDS by Professor Jeffrey Harris, with microscopes provided by Zeiss and a micro-Raman spectrometer provided by Horiba Scientific.

The fifth day was devoted to 15-minute talks by students and early-career researchers providing the latest snapshot of their most recent work.

The Fourth International Diamond School was a fantastic opportunity to learn, exchange ideas, and inspire career choices. GIA’s financial support reduced costs for students, and its sharing of expertise in diamond spectroscopy, diamond treatment, substitution and defect mechanisms, and grading gave the IDS an invaluable industry connection. GIA researchers were active participants throughout the week and inspired the students with their practical experience in the real world of gem diamonds.

The organizers and supporters were especially pleased with the diversity this year. The school had 110 participants from 13 different countries (Canada, Italy, Germany, France, the UK, Austria, the Netherlands, the United States, Russia, Israel, South Africa, Ireland, and Australia). There was a nearly even mix of undergraduate students, Ph.D. students, academic seniors, and industry figures. There was also a nearly equal gender balance, with 45 women and 47 men. @topic:8


Publish Year: 2018 Title: The Beauty of Natural Green Diamonds Abstract: Naturally colored green diamonds are among the most rare and enigmatic of gems, and those with saturated hues—like the stunning examples on our spring issue cover—are highly coveted. Their color origin remains extremely challenging for gemological laboratories to determine.

“Determining origin of color in green diamonds is a major challenge for gemological laboratories.”

In our lead paper, Drs. Christopher Breeding, Sally Eaton-Magaña, and James Shigley review these extraordinary gems, identifying four distinct causes of their green colors— radiation damage defects, luminescence from H3 defects, and absorptions by hydrogen and nickel-related defects— and discuss the difficulties of separating these gems from those colored by manmade irradiation treatments. Using data and observations based on thousands of samples from GIA’s research database, the authors offer an unrivaled gemological characterization of these remarkable gems. We’re delighted to present this article, which is the first in a series on colored diamonds by the same authors.

Our second paper, by Xiayang Lin, Peter Heaney, and Jeffrey Post, investigates the cause of iridescence in metamorphic “rainbow” hematite from Brazil. The authors use electron microscopy, atomic force microscopy, and X-ray diffraction to identify the repeating microstructures responsible for the material’s intense iridescence: oriented arrays of spindle-shaped hematite nanocrystals that form diffraction grating.

In our final feature article, pearl specialists Kazuko Saruwatari, Michio Suzuki, Chunhui Zhou, Promlikit Kessraprong, and Nicholas Sturman apply DNA identification techniques to determine mollusk species by sampling tiny amounts of pearl powder. Their study—using akoya pearls from Ehime Prefecture, Japan—was able to amplify genetic material from this powder and successfully match it with the same gene in mantle tissue from the local Pinctada fucata oyster.

Among the standout topics in our spring issue Lab Notes are entries on CVD synthetic diamonds above three carats, a new Kyocera plastic imitation opal, and a real curio: an extraordinary natural blister “pearl” that formed around a pearlfish. Please explore the inner world of gems with our Micro-World column—this issue we feature a type IIa natural diamond with extraordinary etch channels, an opal with agate-like bands, and a pink tourmaline with spodumene inclusions.

In addition to aquamarine from Pakistan’s Shigar Valley and natural freshwater pearls from Texas, our GNI section showcases the 2018 Tucson gem shows. It summarizes market trends from this year’s show and includes entries on leading jewelry designers, gem artists, and materials such as Russian and Namibian demantoid garnet, fine opal, Oregon sunstone, and turquoise from Arkansas.

Congratulations to the winners of our Dr. Edward J. Gübelin Most Valuable Article Award, announced in this issue. We offer a big “thank you” to all of the readers who voted. Don’t forget to take this year’s G&G Challenge, our annual multiple-choice quiz.

Lastly, please join us for the 2018 GIA Symposium, which takes place October 7–9 in Carlsbad, California. We encourage you to register to attend or submit an abstract for an oral or poster presentation at symposium.gia.edu. @topic:8


Publish Year: - Title: The Magic of Colored Diamonds Abstract: One of the most famous gems in the world, The Hope Diamond is a 45.52 carat Fancy Deep grayish blue diamond. GIA researchers examined it in 1988. Photo: Chip Clark, courtesy of Smithsonian Institution.

Colored diamonds are in the spotlight. They’re routinely breaking records at auction houses. They make headlines when set in celebrity engagement rings. And they’re gemological marvels of the rarest order.
Seen in practically every color of the rainbow, colored diamonds are far rarer than diamonds in the D-to-Z color range. Only one out of 10,000 carats of fashioned diamonds displays fancy color, and a diamond’s chances of displaying intense color are even less – one in 25,000. Browns and yellows are the most common fancy colors. Red, green, purple and orange are the rarest.
GIA® issued its first origin-of-color reports for colored diamonds in 1956. Backed by decades of research and the examination of thousands of colored diamonds, the GIA Colored Diamond Grading System has become the standard for evaluating these extremely rare gems. Current GIA Colored Diamond Grading Reports describe color grades using these terms: Faint, Very Light, Light, Fancy Light, Fancy, Fancy Dark, Fancy Intense, Fancy Deep and Fancy Vivid. Virtually every colored diamond sold at major auction houses has been graded by GIA.

GIA Colored Diamond Reports for natural diamonds provide color grade and color origin (natural vs. treated color), clarity, carat weight, and additional information. Learn more at GIA.edu/colored-diamond-grading
“The GIA Colored Diamond Grading System allows a much more detailed description of diamond color than what had been available under the previous grading system. This has greatly facilitated trading of such stones worldwide, particularly as new sources expanded the quantities of stones in the market and the range of colors,” observed Russ Shor, senior industry analyst at GIA.
Pink
GIA researchers theorize that the color in many pink diamonds is caused by color centers that can selectively absorb light in the visible region of the spectrum. Color centers are the result of lattice defects, or imperfections in the arrangement of atoms in a crystal. These defects can sometimes cause pink graining in the diamond crystal.

The GIA-graded 59.60 carat Pink Star diamond sold for $71 million at the April 4, 2017 Sotheby's auction in Hong Kong. GIA researchers have not definitively determined the origin of this magnificent diamond’s pink color. Courtesy: Sotheby’s
Black
Most naturally colored black diamonds get their color from large quantities or clouds of minute mineral inclusions such as graphite, pyrite or hematite that extend throughout the stone. These diamonds may also have numerous cleavages or fractures that are stained black or have become black because of graphitization. Concentrations of these internal features are responsible for the coloration. However, the actual body color of a natural black diamond may range from near-colorless to brown or “olive” green.

This 67.50 carat black diamond was discovered in India, and was originally 195 carats before being cut into three pieces.
Yellow
The presence of nitrogen causes a diamond to appear yellow. The intensity of the yellow color is dependent upon varying amounts of nitrogen. Yellow diamonds are considered to be a colored diamond and graded as “Fancy” when they fall outside the D-to-Z range (colorless to light-yellow).

This Fancy Intense yellow cushion-cut diamond weighing 54.29 carats is the star in this necklace, while another 67.10 total carat weight of diamonds create a sublime contrast. Courtesy: Chatila
Brown
Once relegated to industrial use, brown diamonds gained cachet in the 1980s when marketers gave them romantic names like champagne, cognac and chocolate. The color in natural brown diamonds is caused by internal parallel brown grain lines due to distortion of the crystal lattice (arrangement of molecules). Brown diamonds are generally more affordable compared to other fancy colors.

18K white gold ring featuring 1.15 carat brown diamond and 0.15 carats of diamonds at halo and shank. Courtesy: TheRealReal.com
Blue
The presence of boron impurities is often responsible for the color of natural blue diamonds. The more boron, the deeper the blue. However, their color can also be caused by radiation exposure or associated with hydrogen. India was historically the source for blue diamonds. Within the last several years, notable blue diamonds have been found at the Cullinan Mine in South Africa.

The flawless, Fancy blue pear-shaped, 13.22 carat Winston Blue, graded by GIA, was sold for $1.8 million per carat at a Christie's May 14, 2014 Geneva auction. Courtesy: Christie’s
Red
Only a handful of red diamonds larger than 5 carats have been found. Red diamonds are so rare that from 1957 to 1987 GIA did not issue a lab report for a diamond with “red” as the only descriptive term. “Predominantly red” means that red is the primary color with no secondary hues (like purple). GIA researchers, who have been studying diamonds for decades and have access to the most sophisticated equipment, are still not sure what causes their color.

The 5.11 carat Fancy red, triangular brilliant cut Moussaieff Red diamond was discovered in 1990 in Brazil.
Green
Green diamonds get their color when radiation displaces carbon atoms from their normal positions in the crystal structure. This can happen naturally when diamond deposits lie near radioactive rocks, or artificially as a result of treatment by irradiation. Naturally colored green diamonds are extremely rare. Because of their rarity and the very real possibility of treatment, green diamonds are always regarded with suspicion and examined carefully in gemological laboratories. Even so, advanced gemological testing can’t always determine color origin in green diamonds. Examined by GIA Researchers in 1988, the 41 ct Dresden Green diamond is the largest, and perhaps the finest, green diamond known to have a color of natural origin.

Examined by GIA researchers in 1988, the 41 carat Dresden Green diamond is the largest, and perhaps the finest, green diamond known to have a color of natural origin.
Synthetic Colored Diamonds
In recent years, gem-quality synthetic colored diamonds have come to market. A Russian company, New Diamond Technology, produced a 10.08 carat diamond with a color grade equivalent to Fancy Deep blue, which GIA examined in September 2016. GIA also offers Synthetic Colored Diamond Grading Reports for synthetic colored diamonds.
Colored diamonds are exceedingly rare and exceptionally beautiful. Because of this, interest in them is not likely to wane. Expect these rarities of the highest order to continue to captivate gem aficionados and the public. @topic:10


Publish Year: 2017 Title: Lizard Skin on Deformed Diamond Abstract: Figure 1. A 2.67 ct oval-cut diamond with uneven “lizard skin” surface texture. Close-up views of the pavilion with reflected light show how the textured pattern continues across facet junctions. Photos by Evan Smith; fields of view 3.56 mm (center) and 1.29 mm (right).
Facets that are nearly parallel to a diamond’s octahedral crystal plane often develop a wavy, rippled appearance called “lizard skin” during polishing (e.g., J.I. Koivula, The MicroWorld of Diamonds, Gemworld International, Northbrook, Illinois, 2000, p. 63). The term is also used more broadly to describe any bumpy, uneven surface texture that develops on polished diamond facets. It is often attributed to polishing off-grain. Recently, GIA’s New York lab encountered a 2.67 ct type IIa diamond (figure 1, left) with especially prominent lizard skin texture on multiple facets (figure 1, center and right). In this case, the texture appears to have developed due to a preexisting deformation fabric or structure inherent to the diamond itself, rather than merely as a consequence of poor polishing technique.

The surface texture has a pattern to it, with small bumps appearing to line up in corridors. Some corridors clearly continue from one facet to the next (figure 1, right). The continuity across facets suggests that this texture is the surface expression of irregularities that actually extend into the volume of the diamond itself. At high magnification with crossed polarizing filters, the lizard skin can be seen to conform to the shape and texture of the strain pattern within the diamond—that is, the pattern of bumps and depressions matches up where the intricate internal dark/light pattern of tatami birefringence meets the polished surface. This connection supports the idea that the surface texture is a reflection of underlying crystal imperfections.

Unusual hydrogen- and methane-bearing metallic inclusions in this diamond suggest it originated from extreme depths of about 360–750 km in the earth’s mantle (E.M. Smith et al., “Large gem diamonds from metallic liquid in Earth’s deep mantle,” Science, Vol. 354, No. 6318, 2016, pp. 1403–1405). In this high-temperature environment, deformation and annealing over a long period of time may have given the diamond a mosaic crystal structure. This natural phenomenon occurs when heat allows the crystal to undergo recovery, a process of dislocation reorganization that divides the distorted grain into a mosaic of smaller, undistorted subgrains without new crystal growth. The subgrains, measuring about 10–30 microns, are like bricks in a wall; while the wall may be slightly curved, the individual bricks are not distorted. These distortions become localized as subgrain boundaries rather than spreading continuously through the crystal. As a result, the subgrains will be oriented in slightly different directions.

Because polishing is so strongly dependent on crystal orientation, if a single facet consists of a mosaic of subgrains with varying orientation, polishing will be uneven. The resulting surface may develop a pattern of bumps and depressions that mimics the size and shape of underlying subgrains and, in turn, reflects the diamond’s natural deformation history. Samples like this one are interesting for scientists because little is known about the geological conditions that lead to the various deformation-related features seen in natural diamonds. @topic:4


Publish Year: 2017 Title: The Foxfire Diamond, Revisited Abstract: Figure 1. The 187.63 ct Foxfire rough diamond. Photo by Jeffrey Post.

The largest gem-quality rough diamond found in Canada, reported earlier in Gems & Gemology (Summer 2016 GNI, pp. 188–189), has revealed remarkable responses to excitation with long- and mid-wave UV light. This 187.63 ct diamond (figure 1) was extracted from the Diavik mine in the Canadian Arctic in the spring of 2015. Aptly named for the aurora borealis, the “Foxfire” displays unusual fluorescence and phosphorescence behavior upon exposure to ultraviolet light. As previously reported, this type Ia diamond has a high concentration of nitrogen impurities, a weak hydrogen-related absorption at 3107 cm–1, and typical “cape” absorption lines.

Exposing this stone to the near-band-gap ultraviolet light of the DiamondView instrument (about 210 nm) and short-wave UV (253.7 nm) results in only very weak fluorescence and phosphorescence, as reported earlier. However, exposure to mid- and long-wave UV (313 nm and 365.0 nm, respectively) produces extremely strong blue fluorescence and strong, long-lived orangish phosphorescence (figure 2).

Figure 2. Left: The Foxfire diamond, photographed in daylight-equivalent lighting. Center: The fluorescence exhibited in a darkened room while the diamond was exposed to long-wave UV. Right: The phosphorescence shown in a darkened room immediately after extinguishing long-wave UV excitation. Photos by Jeffrey Post.

Figure 3. The Foxfire under ambient room lighting, before (left) and just after exposure to long-wave UV light (right). Photos by Jeffrey Post.
Another surprising result of exposing the Foxfire diamond to UV light is a noticeable color change from very pale yellow to a light brown color (figure 3). Fortunately, the diamond reverts to its original color in a matter of minutes in ambient room lighting.

We further examined the spectral characteristics of the UV-excited phosphorescence emission with the spectrometer previously used to study phosphorescence from the Hope and other colored diamonds (S. Eaton-Magaña et al., “Fluorescence spectra of colored diamonds using a rapid, mobile spectrometer,” Winter 2007 G&G, pp. 332–351; S. Eaton-Magaña et al., “Using phosphorescence as a fingerprint for the Hope and other blue diamonds,” Geology, Vol. 36, No. 1, 2008, pp. 83–86). In the present experiments, the UV light sources employed were mineralogical short-, mid-, and long-wave UV lamps. Figure 4 displays the spectral emission between 350 and 1000 nm (approximately 10 nm resolution) as a function of time after turning off the UV light. The most intense emission resulted from long- and mid-wave UV excitation, while phosphorescence excited by short-wave UV was extremely weak.

Figure 4. Phosphorescence emission vs. time after extinguishing long-wave (left), mid-wave (center), and short-wave UV excitation (right)
The spectra of the “orange” phosphorescence reported above are unusual and distinct from those of other natural and lab-grown phosphorescent diamonds we have examined. We speculate that the primary mechanism for phosphorescence in diamonds is light emission resulting from recombination of electrons trapped at ionized donors and holes trapped at ionized acceptors that are in close proximity to one another. The long time delay results from the thermal movement of the trapped electrons or holes to retrap close enough to one another (P.J. Dean et al., “Intrinsic and extrinsic recombination radiation from natural and synthetic aluminum-doped diamond,” Physical Review, Vol. 140, No. 1A, 1965, p. A352–A386; B. Dischler et al., “Diamond luminescence: Resolved donor-acceptor pair recombination lines,” Diamond and Related Materials, Vol. 3, 1994, pp. 825–830). In the case of the Foxfire, we cannot identify as yet the nature of either the acceptors or donors involved.

Similarly, the phenomenon of the observed color change from light yellow to light brown with UV excitation and the reversal to light yellow has no detailed explanation yet. Such color changes, or sometimes a lightening of color, are often observed in natural diamonds. It is speculated that these are due to charge transfer between various defects (donor or acceptor states) within diamond. Diamond is inherently an insulator where electric charges move very slowly and their motion depends on the nature of the defects present, the temperature of the diamond, and its exposure to light. For an interesting discussion, see K.S. Byrne et al., “Chameleon diamonds: Thermal processes governing luminescence and a model for the color change,” Diamond and Related Materials, Vol. 81, 2018, pp. 45–53. @topic:4


Publish Year: - Title: Diamond Buying Tips Abstract: A pair of diamond earrings are a classic gift to mark a special occasion.

Jewelry is one of the most popular gifts we use to mark the momentous occasions in our lives. It is an outward expression of what we mean to one another. Holidays, birthdays and anniversaries and other

achievements are just some of the events we celebrate with special gifts of jewelry, and diamonds are among the most favorite to give.

The budget for your gift is likely one of your most important parameters, but you can make sure you receive the most value for your purchase by learning more about diamonds before you shop. These six tips will help you find your ideal

gift.
Learn about the 4Cs
The 4Cs of diamond quality is a language jewelers everywhere use to describe the attributes of a diamond, that when taken together, help to determine its overall quality. Quality is ultimately tied to price,

so it’s crucial that you learn the 4Cs so that you understand what you’re buying:
Carat

Clarity
Diamonds are created by nature under tremendous heat and pressure. Nearly all diamonds contain unique internal characteristics called inclusions and external characteristics called blemishes. Many clarity

characteristics are too tiny to be seen by anyone other than a trained gemologist using magnification. The GIA Clarity Scale contains 11 grades ranging from

Flawless to Included.

Color
Truly colorless diamonds are very rare and highly valued. The GIA Color Scale uses letters to represent the absence of color,

beginning with D (colorless) and ending at Z (light yellow or brown). Color distinctions can be quite subtle and only visible to the trained eye, but the differences can have a significant impact on price.

Cut
While diamonds can be fashioned into different shapes, the term “cut” refers to how a diamond’s complex proportions and angles relate to light. A number of factors influence a diamond’s

cut grade, including its overall face-up appearance, design and craftsmanship. The GIA Cut Scale for standard round brilliant cut diamonds ranges from Excellent

to Poor.

Choose a trained jeweler
Select a jeweler as carefully as you do a doctor, lawyer or any other trained professional. Find someone who is credentialed, such as a GIA Graduate Gemologist. Take note of their affiliations with jewelry

industry groups and professional associations. Use GIA’s Retailer Lookup to find a jeweler near you who carries GIA-graded diamonds or has GIA-trained associates on staff.
Ask for an independent diamond grading report
A diamond grading report is an unbiased assessment of the diamond’s quality. It provides a description of the diamond’s 4Cs and confirms that the stone is a natural or synthetic diamond. The report

also discloses any treatments the diamond may have undergone to alter its color or clarity. You can verify the information contained in any GIA report by entering the report number in Report Check, GIA’s secure online database.

sample Diamond Dossier." title="GIA diamond grading reports, like this Diamond Dossier®, provide a full assessment of a diamond’s quality using the 4Cs. View a sample Diamond Dossier." />
		GIA diamond grading reports, like this Diamond Dossier®, provide a full assessment of a diamond’s quality using the 4Cs. View a sample Diamond Dossier.
Keep your purchase secure
A laser inscription will help identify your diamond if it’s ever lost or stolen. You can request to have the diamond’s report number or a personal message inscribed on the girdle (the

diamond’s perimeter). The inscription is viewable using a jeweler’s loupe or microscope under 10X magnification. Diamonds that come with GIA Diamond Dossier® reports contain the diamond’s report number laser

inscribed on the girdle.

Microscopically inscribing the report number on the diamond’s girdle makes it possible for you to easily identify your diamond in case it is ever lost or stolen.
You should also have the diamond appraised and insured. A diamond grading report is the independent assessment of quality, while an appraisal gives a monetary value. If you’re looking for a qualified

appraiser, you might start by contacting an appraisal

organization for a referral.
Consider purchasing the diamond loose and having it set in the ring later
Are you shopping for an engagement ring, but not sure what your future fiancée prefers in a ring? Consider purchasing a loose diamond and then decide on the mounting together. Make sure to have the

loose stone graded before having it mounted. Read more engagement ring buying tips.
A final tip before you head for the jewelry stores

Be sure to download GIA’s free 4Cs app for a convenient way to have more diamond knowledge at your fingertips, including access to GIA’s Retailer Lookup and Report Check services. Available in English and Simplified Chinese,

you can find GIA’s 4Cs app on iTunes for iPad (English) (Chinese) or iPhone (English) (Chinese) and on Google Play (English) (Chinese). @topic:10


Publish Year: - Title: The Latest on Synthetic Diamonds Abstract: The largest blue HPHT synthetic diamonds to date: a 5.26 ct heart shape and a 5.27 ct emerald cut. Both were graded as Fancy Deep blue. Photo by Terry Poon.

Dr. James Shigley, GIA distinguished research fellow, is one of the foremost experts in diamonds and their identification. In this presentation recorded at the 2017 JCK Las Vegas show, he shares the latest developments about HPHT and CVD synthetic diamonds, and information on GIA’s ability to identify them.
Gem quality synthetic diamonds became commercially available in 1986. Since then, the production and quality have steadily increased. “Synthetic diamonds have a place in the market as long as they are properly disclosed at the time of sale,” Shigley said. The increased use of synthetic diamonds, also referred to as laboratory grown or manmade diamonds, in jewelry and their marketing to consumers make accurate identification and disclosure even more important, so buyers can make informed decisions.

Synthetic diamonds have a place in the market as long as they are properly disclosed at the time of sale.
Dr. James Shigley, GIA distinguished research fellow

GIA’s research teams have years of experience examining natural and synthetic diamonds. That research, coupled with advanced technology, enables GIA to positively identify manmade diamonds, separating them from natural gems. In addition to screening every diamond submitted for grading to confirm its origin as natural or lab-grown, the Institute offers a specialized service to screen parcels of melee (small diamonds that are approximately 0.005 to 0.25 ct used in jewelry), offering clients an extensive analysis that differentiates natural diamonds from synthetic diamonds. Shigley also discusses the GIA iD100™, a new instrument that definitively separates natural diamonds from synthetic diamonds.

	The Latest on Synthetic Diamonds

Shigley received his undergraduate in geology from the University of California, Berkeley and his doctorate in geology from Stanford University. He joined GIA in 1982 and helps direct GIA’s research activities in the identification of diamonds and colored gemstones. He has represented the Institute’s work around the world, giving lectures and publishing his research. @topic:4


Publish Year: - Title: The Unexpected Origins of Big Diamonds Abstract: 23.16 carat pink diamond unearthed from the Williamson Mine in Tanzania. Image courtesy of Petra Diamonds.

Dr. Evan Smith, Ph.D., GIA research scientist, has dedicated his work to methodically characterizing the inclusions found in rare diamonds. In this video presentation recorded at the 2017 JCK Las Vegas show, Smith shares his findings on the unexpected origins of big diamonds and what their characteristics tell us about the earth.
“Next time you look at a diamond, I hope you see it not only as a beautiful, valuable piece of gemstone; [you should also know that] diamonds are some of the most scientifically valuable samples of our earth,” Smith said. In this video, he explains that as diamonds form more than 100 miles below the earth’s surface, they often trap mineral inclusions that reveal the chemistry of the earth’s mantle.

Diamonds are some of the most scientifically valuable samples of our earth.
Dr. Evan Smith, GIA research scientist

Smith’s study on a 400 carat diamond found in Angola was the December 2016 cover story of Science magazine. Big diamonds such as this were the basis for his research in part because the origins of big stones are relatively unknown to scientists. He examined a variety of large, unique diamonds with similar characteristics. The diamonds were all similar to the Cullinan diamond, the largest gem quality diamond ever found. They were large and inclusion poor, typically without mineral inclusions; pure type IIa diamonds low in nitrogen; irregularly shaped and resorbed with surfaces rounded and dissolved. These characteristics gave rise to their name – CLIPPIR diamonds.

	Origins of Big Diamonds

An expert in diamond geology, Smith received his bachelor of applied science and master of engineering from Queen's University and a Ph.D. in geology from the University of British Columbia. He performed his postdoctoral research fellowship at GIA in 2015. @topic:8


Publish Year: - Title: 10 Diamonds That Dazzled at Auction Abstract: This 5 carat, cushion-shaped Fancy Vivid pink diamond set in platinum and 18k rose gold sold for $10.83 million at a December 2009 Christie’s auction in Hong Kong. Photo courtesy Christie’s

	The world has seen many impressive – and even historic – diamonds offered for sale at auction in recent years. The photo gallery above highlights 10 that have enthralled diamond connoisseurs with their extraordinary size, striking cut, flawless clarity, perfect color and the most alluring feature of all: rarity. These diamonds are the pinnacle of the beauty and allure of gems.

View Gallery

Read more about the growing influence of auction houses on the colored gem and diamond industry in the Spring 2013 issue of Gems & Gemology.

All of the diamonds in this photo gallery have been graded by GIA. @topic:7


Publish Year: - Title: Synthetic Diamonds: How Many Are Out There? Abstract: GIA research scientist Sally Eaton Magana analyzes the image of a marquise diamond in the DiamondView to determine whether or not the stone is synthetic. Photo ©GIA.

Another report of a gemology lab spotting a parcel of undisclosed synthetics has prompted renewed questions about how many synthetics may have infiltrated the gem market – and there is considerable disagreement.

One estimate by Tacy Ltd. said that more than $700 million worth of synthetics – disclosed or not – entered the jewelry market last year. De Beers, on the other hand, while not providing a dollar amount, claims that only a fraction of that figure is in the market. De Beers said it bases its opinion on the costs involved in producing both Chemical Vapor Deposition (CVD) and High-Pressure, High-Temperature (HPHT) synthetics, both of which it manufactures through its Element Six division.

GIA has seen no appreciable upturn in the numbers of synthetics to its lab, disclosed or not, said Tom Moses, senior vice-president of Laboratory and Research.

The controversy over undisclosed synthetics is generally focused on smaller diamonds (under 0.30 carats) that are less likely to be submitted to GIA or other gemological labs. While there is ample evidence that Fancy yellow and yellowish brown melee-sized HPHT synthetics have been in the market for some time (Gems & Gemology, Fall 2008), small CVD colorless synthetics offer very little price advantage over natural diamonds because of high production costs, according to Stephen Lussier, Executive Vice President, Marketing, De Beers Group; CEO, Forevermark who was interviewed last Spring. He believes the majority of undisclosed small CVD synthetics are by-products of large pieces created for industrial uses and believes that those turning up in labs are still “isolated examples.” CVD-grown diamonds are type IIa, free of nitrogen that can add color, which makes them useful for optics and electronics.
The technology to create CVD synthetics, however, is improving, which means their numbers in the market may increase. Dr. James Shigley, GIA’s Distinguished Research Fellow, notes that recent samples he has examined show no signs of post-production treatment. Earlier CVD synthetics often came out gray colored and required costly heat treatments to improve their color. Eliminating post-treatment heat processing cuts costs considerably, but also lessens the risk of damage to the newly made stones.

De Beers, Lussier said, is preparing a defense against undisclosed synthetics in the form of a mass-screening device to fast-check melee for synthetics. The unit is in testing. Earlier this month, the company reported that it had tested numerous parcels of melee on behalf of its clients and found no synthetic diamonds.

One recent synthetics-sighting was in a group of 18 type IIa Fancy brown stones, ranging from 0.14 to 0.63 carats, that a dealer purchased in hopes of improving the color through HPHT treatment. The treatments were unsuccessful, however, prompting the dealer to send them to a lab for examination. The lab reported that 13 of the stones were CVD synthetics.

GIA researchers continually test synthetic samples with the De Beers’ DiamondSure, which can flag all synthetics, along with some types of treated diamonds, and also a small percentage of natural diamonds. Stones that are referred by the DiamondSure as possibly synthetic have spectra collected by advanced testing instrumentation and are typically screened by the larger DiamondView, which provides an extremely detailed fluorescence image that GIA researchers use to  identify whether the diamond is natural or synthetic.

GIA researchers perform a battery of additional tests on all “referred” diamonds to be absolutely certain of a diamond's origin.

The DiamondSure is the one of the first tests a diamond will receive after submission to GIA labs. If the diamond is Type II and shows certain characteristics, the DiamondSure will refer the stone to the DiamondView for further testing. Photo ©GIA.

The DiamondView enables lab staff to view tell-tale growth patterns for synthetic diamonds. The regular striations visible in the middle of this round diamond indicate it is a CVD-grown synthetic. Photo ©GIA. @topic:4


Publish Year: - Title: How Does Light Affect How My Diamond Looks? Abstract: GIA’s Diamond Cut Grading system for round brilliant diamonds includes seven components: brightness, fire, scintillation, weight ratio, durability, polish and symmetry. Fire is well illustrated in these loose diamonds that range in size from 2 to 3.03 carats. Photo by Harold & Erica Van Pelt/ GIA

                      If you’ve ever wondered why your diamond looks different in sunlight versus candlelight or daylight versus office lights, it’s because the cut of your diamond responds differently depending on the light and the environment you are in. How – and where – you look at your diamond can greatly change its appearance.

Al Gilbertson, a GIA researcher, says if you think of a diamond like “a series of mirrors reflecting its environment,” it can help you understand how light and location can change the way your diamond appears. When you look at your diamond, you are also seeing a reflection of the surrounding environment, including yourself.

“Often times, the dark parts of the pattern you see in a diamond are a reflection of your face, or the camera – if you’re looking at a photograph,” Gilbertson says. “You can test this yourself. Hold the diamond at arm’s length and look at how bright it is and how the pattern of dark and light appears. Now, gradually bring it closer to your eye. By the time it gets very close, the area of dark pattern in the diamond has grown and is much more prominent.”

“This all means that in every different location you look at your diamond, this ‘series of mirrors’ is reflecting not only the environment, but also you. How close you hold it, and the environment you are in, affects the pattern you see.”

When it comes to the 4Cs of GIA’s Diamond Grading System – color, clarity, cut and carat weight – cut is often the least understood because there are so many components considered in the cut grade. The first three – brightness, fire and scintillation – describe the diamond’s appearance. The remaining four components – weight ratio, durability, polish and symmetry – describe the design and craftsmanship.

Each cut grade – excellent, very good, good, fair and poor – represents a range of proportion sets and diamond appearances. There is no single set that defines a well-cut round brilliant diamond – many different proportions can produce attractive diamonds, which should be bright, fiery, sparkling and have a pleasing overall appearance, especially when the pattern of bright and dark areas is viewed face up, Gilbertson says.

GIA’s Diamond Cut Grading System for standard round brilliant diamonds in the D-to-Z color scale and the Flawless-to-I3 clarity range provides an objective assessment of a diamond's overall cut quality.

GIA studied diamond cut for decades and analyzed tens of thousands of proportion sets before the system was introduced in 2005. It had to be scientific, but also practical and applicable to the jewelry industry and public. There were more than 70,000 observations of 2,300 diamonds in studies conducted across all sectors of the jewelry industry – diamond manufacturers, dealers, retailers and potential customers.

	GIA analyzed tens of thousands of diamonds and proportion sets – and conducted studies with members of the jewelry industry – before the cut grade system was introduced. Photo by Robert Weldon/GIA
Diamonds graded in GIA’s laboratories are examined in standardized and calibrated environments – scales for carat weight, optical measuring equipment for all of the diamond’s proportions, light for color grading and 10X loupes for clarity, polish and symmetry help ensure consistency and objective grading.

Most people won’t ever see the diamond in a laboratory, so what type of lighting is best when purchasing a diamond? Gilbertson encourages you to look at the diamond in the type of lighting you will most typically wear it.

GIA’s Cut Grade System offers a description based on research and what most people prefer. But Gilbertson likes to remind people that diamonds are more than that.

“Diamonds and jewelry are very personal,” he says. “People buy jewelry for themselves or receive it as a gift for a specific reason, often to celebrate a special occasion. Choose what you like and what looks best in your opinion. Then, enjoy the adventure of learning all the different appearances your diamond can have.”

	From left: These diamonds display high, moderate and low brightness under fluorescent light. Photos by Eric Welch/GIA @topic:10


Publish Year: 2016 Title: Examination of the Largest Canadian Diamond Abstract: With the first major discoveries made 25 years ago, diamond mining in Canada is relatively new. The Diavik mine, located in the Northwest Territories about 300 kilometers (190 miles) northeast of Yellowknife, began production in 2003. Today Diavik is Canada’s largest diamond mine by volume, producing approximately six to seven million carats of gem-quality diamonds annually. Much has been reported about Diavik’s extensive efforts (see the lead article of the Summer 2016 issue) to ensure the long-term protection of the land, water, and wildlife that are integral to local traditions and daily life in the Northwest Territories.

	Adding to the significance of the Diavik mine was the spring 2015 recovery of the largest rough diamond ever found in Canada. GIA’s laboratory in New York recently had the opportunity to study this historic stone. The rough weighed 187.66 ct and measured 36.96 × 32.99 × 16.80 mm. Under standard color grading lighting conditions, it appeared pale yellow (figure 1). One side of the diamond displayed clear iridescent color banding due to light interference along the cleavage planes (figure 2, left). The stone showed irregular morphology, with a tabular shape, and was dominated by cleavage faces. Some original faces with dissolution pits were clearly visible (figure 2, center).

Figure 1. This pale yellow type Ia “cape” diamond from the Diavik mine, weighing 187.66 ct, is the largest Canadian diamond to date. Photo by Sood Oil (Judy) Chia.

	When observed under a gemological microscope, the irregular surface etching limited our ability to see clearly into all areas of the diamond. A dark mineral inclusion was noted near one side of the rough (figure 2, right), but little else was readily apparent. Crossed polarizing plates did not reveal any areas of strain. The stone exhibited moderate blue fluorescence to long-wave UV radiation and faint yellow fluorescence to short-wave UV; no phosphorescence was observed. Absorption spectroscopy in the infrared region revealed that it was a type Ia diamond with a very high concentration of nitrogen. A weak hydrogen-related absorption at 3107 cm–1 was also recorded. UV visible absorption spectroscopy, performed at liquid nitrogen temperature, showed typical “cape” lines, with clear absorption peaks at 415 and 478 nm. No other absorption was detected in the UV-Vis region. These gemological and spectroscopic observations confirmed that this was a natural, untreated diamond.

	Figure 2. Iridescent color can be seen along the cleavage plane on one side of the stone (left). Dissolution pits are observed on the surface of the yellow rough (center), and a dark mineral inclusion is clearly visible near the surface (right). Photomicrographs by Kyaw Soe Moe; field of view 14.52 mm (left), 4.79 mm (center), and 7.19 mm (right).

	The diamond, named the Diavik Foxfire, will undergo further scrutiny during the cutting process, in which it will be carefully designed, shaped, faceted, and polished. It will be interesting to see if the rough yields a significant main diamond or is cut into several smaller gems. @topic:10


Publish Year: - Title: Secrets to Keeping Your Diamond Sparkling Abstract: The sparks will fly − and your diamond will shine − when you follow these cleaning tips.

	Diamond is the hardest natural substance on Earth. It can cut any kind of rock or metal, but only another diamond can cut a diamond. In fact, to burn a diamond, it must be heated to between 1290-1650 degrees Fahrenheit. Yet the oil deposited from the mere touch of a human finger can cause dirt to collect and make this nearly indestructible gemstone quickly lose its sparkling appeal.

	So how can you keep your diamond looking its very best? Here are some tips on keeping your diamond sparkling.

	Handle your diamond sparingly

	Diamonds are natural magnets for grease, so they’re not easy to keep clean. When a diamond is handled, the oils from your fingers adhere to the diamond’s surface and affect its brilliance and fire.

	Clean your diamond regularly

	A simple plan to keep your diamond jewelry looking beautiful is to soak it in a gentle degreasing solution, such as water with a few drops of mild dish soap, once or twice a week. After you remove the diamond from the cleaning solution, use a soft, clean toothbrush to remove any remaining dirt. The toothbrush should be new and reserved exclusively for cleaning your jewelry. Use it to clean hard-to-reach places like the back of the diamond, which tends to collect the most oil and dirt.

Scrubbing your jewelry with a soft, clean toothbrush helps remove leftover dirt. Just be sure not to use on jewelry that is too fragile, such as estate jewelry, to avoid any potential damage. Photo by Eric Welch/GIA

	Use a gentle touch

	Fragile settings, like older prongs in antique jewelry or a tension setting where the diamond is held in place by pressure from the shank, shouldn’t be vigorously scrubbed, so be gentle with the toothbrush. Then, just rinse your diamond jewelry with water and dry with a soft, lint-free cloth. If you’re working over a sink, make sure to close the drain.

Lint-free cloths, such as this gem cloth, are ideal for removing oily film and dirt. Similar cloths are available at most hardware stores or through the GIA store.

	Don’t use harmful solutions

	Chlorine bleach or abrasives (such as household cleansers or toothpaste) should never be used when cleaning diamond jewelry. Chemicals like chlorine can damage some of the metals used to alloy gold for diamond settings and abrasives can scratch gold and other metals.

	Use ultrasonic cleaners with caution

	Sometimes an ultrasonic cleaner is necessary to remove encrusted dirt on diamonds. By sending low frequency sound waves through a solution, ultrasonic cleaners cause vibrating fluid to remove accumulated dirt and grime. But they can also shake loose stones from their mountings or chip the girdles of diamonds that are set next to each other. Proceed cautiously if the diamond contains feathers or is included, and avoid ultrasonics if the diamond has been treated by fracture filling.

Ultrasonic cleaners are used to remove heavy dirt and grime, but could cause damage depending on the stone, treatment or setting. It’s best to have your jeweler clean your jewelry using these machines to avoid any damage.

	Before placing your diamond in an ultrasonic cleaner, it’s best to refer to the diamond’s grading report, which clearly discloses whether the diamond has been treated. You should also consult a professional jeweler who can determine if your jewelry needs repair, such as checking for loose stones and tightening them, before it is cleaned.

	The key to a diamond’s sparkle lies in its facets – which work like a series of many tiny mirrors reflecting light in and out of the stone. Regularly cleaning the facets will keep your diamond sparkling and your diamond jewelry in gleaming condition, ready to shine for your next special occasion.

	Want to know more about how to clean and protect your jewelry? Read Tips on Caring for Your Jewelry. @topic:10


Publish Year: - Title: How to Protect Your Diamond from Chipping Abstract: Diamonds are known for their hardness – their ability to resist scratches and abrasions.  But diamonds are not impervious to damage, since their hardness is uneven along different crystal directions. This image shows a 1.05 ct diamond with a chip starting at its girdle, extending to the culet. Photo © GIA.

	DIAMOND DURABILITY

	Gems are valued for their beauty, rarity, and durability. Durability is a gemstone’s ability to withstand wear, heat, and chemicals. The concept of durability consists of three properties:

		Hardness: How well a gemstone resists scratches and abrasion

		Toughness: How well a gemstone resists breaking and chipping

		Stability: How well a gemstone resists chemicals and thermal shock

	Diamond is very stable and extremely hard, but only somewhat tough. The hardness is uneven along different directions of the crystal, and this has important implications both for the cutting process and the durability of diamonds cut in various shapes.

Hardness
	The hardness of a diamond is a result of its very compact crystal structure. “Diamond has an indentation or scratch hardness five times that of carbides. [Figure 1] illustrates the hardness of diamond compared to other materials according to both Moh’s [sic] and Knoop’s hardness scales. However, diamond is relatively brittle and will chip or fracture if it is not handled and protected against shock” (V.C. Venkatesh and S. Izman, Precision Engineering, 2007, p. 50). Diamond is the hardest known natural mineral on both the Mohs and Knoop scales, which characterize a mineral’s scratch resistance through the ability of a harder material to scratch a softer material.

	Figure 1. A comparison of the Mohs hardness scale and the Knoop hardness scale, a
	micro-hardness test where a pyramidal diamond point is pressed into the polished
	surface of the sample with a known load for a specified time and the resulting indentation
	is measured with a microscope. Illustration modified from V.C. Venkatesh and S. Izman,
Precision Engineering, 2007, p. 50.

Stability
	Diamonds are very stable and invulnerable to virtually all acids. They can also withstand higher temperatures than most gemstones. Sudden extreme temperature changes can cause damage, however.

Toughness
	Diamonds can chip or fracture from hard impact, especially in areas where the carbon atoms are not tightly bonded. These areas, called cleavage planes, are the major source of damage to diamonds (figure 2). The toughness scale used in scientific literature is called a fracture toughness scale, but it is rarely mentioned in gemology. The toughness scale measures (in erg/cm2) the work required to separate two surfaces of a crystal along a certain crystallographic plane. Values for diamond generally range from 5,000 (along the cleavage planes) to over 8,000 (in the “hardest” direction). Compare those values to 225,000 for nephrite and 120,000 for jadeite, which are tougher, and 600 for corundum, which is not as tough.

Figure 2. Atoms of carbon are arranged in very tight rows. In the directions where carbon atoms are most compact, it is very difficult to break a diamond. Note that atoms also lie in planes. The distances between planes are greater than the other distances between the carbon atoms. In the directions where the atoms lie in planes, diamonds can break, though with some difficulty. Those directions are referred to as cleavage planes. Illustration by Al Gilbertson, © GIA.

	TOUGHNESS: THE ACHILLES HEEL OF DIAMOND

	Even though diamond is the hardest natural material, it can chip and fracture in the course of normal wear. Diamond is formed in the cubic crystal system and has four perfect cleavage directions. A cleavage plane is the weakest direction in the molecular arrangement of the crystal. Diamonds are tougher in the directions where the atoms are bonded tightly together, less tough where they’re not so tightly bonded. The most common form of the natural diamond crystal is an octahedron (figure 3), and our focus will be on that typical shape. Cleaving is the splitting of a diamond crystal parallel to one of its triangular, octahedral planes. While not the perfect example, compare wood, which has a single grain typically split by an axe with ease. A natural diamond crystal can only be cleaved parallel to one of the triangular octahedral faces (figure 4).

Figure 3. Idealized octahedron. Illustration by Al Gilbertson, © GIA.

Figure 4. Cleavage planes are parallel to the triangular octahedral face. Illustration modified from V.C. Venkatesh and S. Izman, Precision Engineering, 2007, p. 54.

	Because diamonds are harder and tougher along certain directions of the octahedral crystal, they are also more resistant to chipping, abrasion, or cutting with other diamonds along these directions (figure 5). There are also softer directions (figure 6). For some of the famous historical diamonds, months were spent planning before cleaving because the external partial crystal form obscured the octahedral directions.

Figure 5. These are the hard directions in diamond crystals, the most difficult ones for the cutter to work with. Illustration by Al Gilbertson, © GIA.

Figure 6. These soft directions are easier for the cutter to work with. Illustration by Al Gilbertson, © GIA.

	Diamonds are rarely cleaved today. Usually they are sawn and, more recently, cut by laser. However, cutters still need to understand the hard and easy directions of polishing as well as the location of cleavage planes in order to plan cutting. An octahedron generally yields a round brilliant from a certain location within the crystal (figure 7).

Figure 7. When cut from the octahedral crystal, the outer edge of the round brilliant would nearly touch the outer edge of the original octahedron. Illustration by Al Gilbertson, © GIA.

	During the planning stage, a saw is used to cut off the top portion, which can be used to cut another diamond. Note that the typical crown (top) of a round brilliant is slightly higher than the typical crown of a princess cut. If the cutter wants to create two princess-cut diamonds from a crystal, the planning is slightly different than when two rounds are being cut (figure 8).

Figure 8. When sawn, the lower plane (lower red line) will eventually yield two princess-cut diamonds. If the crystal were being cut to yield round brilliants, the sawing line would be the higher line (upper red line). Illustration by Al Gilbertson, © GIA.

	Remember that diamonds are tougher in the directions where the atoms are bonded tightly together, less tough where they’re not so tightly bonded. Look at the location of the corners on a princess cut, which are very vulnerable to chipping since they lie close to the cleavage plane. Cutting styles like these, with pointed corners or ends, are often set with prongs to protect the corners from chipping. Even still, a hard blow to a prong at a corner of a princess cut (figure 9) can cause a chip to run down the side of the diamond. This is not exactly at the cleavage plane, where the carbon atoms are farthest apart, but very near it. When chips occur, they rarely look like smooth flat planes of cleavage. Rather, they appear to be stepped, because they are not directly on the cleavage plane (figures 10 and 11).

Figure 9. The corners of a princess cut are very vulnerable to chipping since they lie close to the cleavage plane. Illustration by Al Gilbertson, © GIA.

Figure 10. The chip at the corner of this princess-cut diamond has a stepped look since it is near but not directly at the cleavage plane. Photo by James Gibson, © GIA.

Figure 11. Chips typically have a stepped appearance. Photo by Mitch Lam, © GIA.

	HOW TO MINIMIZE THE RISK OF DIAMOND CHIPPING

	Chips typically occur when the girdle (edge) or point of a diamond strikes something hard. Bathroom and kitchen countertops, as well as jewelry items with diamonds worn next to each other, are common causes of chips.

1. Avoid shapes with points or sharp corners
	Any shape of diamond with points or sharp corners is more exposed to chipping at those locations (figures 11 and 12). Round, oval, and rounded-corner cushions don’t have that point exposure. A more recent cutting technique called chamfering is used by some in the diamond trade and believed to improve durability for princess cuts. Chamfering places a very small flat facet on the corners (figure 13).

Figure 12. Corners for emerald cuts, triangular shapes, radiants, and princess cuts are at higher risk and need adequate girdle thickness to minimize their exposure to chipping. Here an extra facet at the corner of a princess cut brings that corner to a sharp point, resulting in a very high risk of being chipped. Photo by James Gibson; illustrations by Al Gilbertson, © GIA.

Figure 13. A chamfered corner on a princess cut is so small that most cannot see the small facet without magnification. Photo by Jonathon Muyal, illustrations by Al Gilbertson, © GIA.

2. Protect the culet
	At one time, almost all standard round brilliant cut diamonds and many other shapes were cut with a small facet at the culet. This was to protect the culet from chipping. Now most diamonds come to a sharp point at the culet, and thus all culets with points are vulnerable (figure 14). Once they are set in jewelry, however, there is little risk of damaging the culet.

Figure 14. Pointed culets are vulnerable to chipping when diamonds are loose and strike against each other in stone papers. Photo by James Gibson, © GIA.

3. Avoid girdles with very thin sections
	While a strong blow can break a diamond at the girdle, a thicker girdle is more difficult to chip. Girdles with very thin places along the sides or at the corners and points are at a much higher risk of damage (figures 15 and 16).

Figure 15. Extremely thin girdles are at extreme risk of being chipped. Here, a marquise has a knife-edged portion of a girdle that could be chipped very easily. Photo by Leo Ochoa, illustrations by Al Gilbertson, © GIA.

Figure 16. This emerald cut with an extremely thin girdle has two chips. Photo by Leo Ochoa, illustrations by Al Gilbertson, © GIA.

4. Chose a setting that protects the diamond
	Vulnerable points or corners are better protected with bezels, partial bezels, or V-shaped prongs.

5. Use caution with tension settings
	A tension setting holds a diamond in place using a groove cut into the metal that the girdle fits into, and the two ends of the ring press tightly against the diamond’s sides. A jeweler with experience in tension settings will be very careful about the condition of the girdle before allowing a diamond to be set in this manner.

	The mounting is already exerting pressure on the diamond at two opposing locations on the girdle. Hitting the side of the ring puts even more stress on the girdle. This style also leaves the exposed sides of a diamond vulnerable to damage just during casual wear.

6. Regularly inspect prongs for damage
	A very common cause of chipping is that the prongs holding the gem in place in a piece of jewelry become bent or broken. If a diamond is loose in the mounting, it is at higher risk of getting chipped. Prongs protect their corners, points, and sides. If the prongs become bent or broken due to wear and tear, they are not doing their job: protecting your diamond.

	Even if only one prong is damaged, your diamond is no longer held securely in its mounting.

7. Don’t wear a diamond that has already chipped
	If a diamond already has a chip, some think they can take care of the mounting later. That knife-edged portion of the diamond that is chipped has an extremely high risk of getting chipped far worse. Stop wearing it until you can have it repaired.

8. Be careful with inclusions near the girdle
	It’s rather obvious that a diamond with many inclusions located near the girdle and/or points is rendered more prone to chipping or breaking. But sometimes there can be a small feather or other small inclusion near the girdle or point that also makes the diamond vulnerable (figures 17 and 18). If the stone is hit precisely on a feather or inclusion near the direction of a cleavage plane or at a point, a chip is likely to occur. Open cavities at the girdle are much like chips and are more easily damaged (figure 19).

	Figure 17. The small cluster of feathers at the corner of this princess cut poses a high risk
	for damage when setting the diamond or when it is being worn. Photo by Mitch Lam, © GIA.

	Figure 18. The corner of this radiant cut has a large feather that places it at risk for further
	damage. Photo by Mitch Lam, © GIA.

	Figure 19. The open cavity at the girdle makes this thick girdle more susceptible to chipping. Photo by Mitch Lam, © GIA.

	There is no such thing as perfect toughness. Any gem will break, not just chip, if it is hit hard enough. Diamonds are very tough, but remember that if a cutter can purposely cleave (split) a diamond by giving it a sharp blow in the right direction, you can achieve the same thing if you hit it hard enough accidentally. You are more likely to damage a diamond at the girdle or at a point. Diamonds with exceptionally thin places on their girdles are very vulnerable. To avoid damage, you should only wear your diamond jewelry during activities where you are unlikely to hit them hard against solid objects. @topic:4


Publish Year: - Title: Diamonds from the Roof of the World Abstract: Lesotho’s remote Maluti Mountains are the most picturesque portion of this landlocked country, which is totally enclosed by the Republic of South Africa. These mountains are also the source of some of the world’s most coveted type IIa diamonds and large diamond crystals. Photo by Robert Weldon/GIA

                      Eight years ago, a worker pulled a huge crystal from the sorting area of the Letseng Mine in Lesotho. The rough diamond weighed in at just over 603 carats (cts), making it the 15th largest ever found by anyone, anywhere. The mine’s majority owner, London-based Gem Diamonds, named it the Lesotho Promise in recognition of the nation from whose soil it was unearthed.

For Mazvi Maharasoa, CEO of Letseng Diamonds, a partner in the mine, that diamond and the three 450 ct-plus diamonds that have been found there since are more than a promise—they are a source of national pride and a promise realized.

“This mine is unique, producing the highest average value diamonds ($2,043 per ct, against the global average of $106 per ct) in the world,” she says. “Lesotho is a dot on the map to some people, but these diamonds have brought us recognition.”

The mine is also one of the world’s largest sources of highly coveted type IIa diamonds. Normally, such stones comprise about 2% of diamonds recovered worldwide, but at Letseng, they are about one-quarter of the output.

Touring the mine, located about 3,100 meters (just over 10,000 feet) high in rugged mountain country, Maharasoa notes, “This mine came from nothing in 2000. Now we have 1,500 employees (and) a mine that gives our country 70% of its corporate tax revenue and 60% of our country’s foreign exchange earnings.”

Maharasoa was born in the capital city of Maseru and earned a degree in international and commercial law from the University of Buckinghamshire, north of London. She returned to Lesotho as legal advisor to the Ministry of Natural Resources.

“This is when I became acquainted with the diamond area,” she says, adding that negotiations over changes in the diamond laws and a new contract to restart Letseng were part of her work.

	Mazvi Maharasoa, CEO of Letseng Diamonds. Photo by Russell Shor/GIA
Restarting production at the mine was a challenge. The kimberlite was discovered in 1957 by South African geologist Peter Nixon deep in the Maluti Mountains, amid farming villages and shepherd huts where it seemed that time had stood still for a millennium. It wasn’t until the following year that two South African prospectors, Keith Whitlock and Jack Scott, set out in search of diamonds. They endured extreme cold and blizzards and returned with about 1,800 cts of diamonds.

For several years, the government allowed artisanal miners to file claims and work the site, but in 1968, it invited the mining giant RTZ (now Rio Tinto) to prospect the area. The company worked to develop the mine for four years but determined that the grade of the ore (less than two cts per 100
tons) was too low to mine profitably.

After RTZ moved on, the government invited then-De Beers chairman Harry Oppenheimer to have a look. As a result of his visit, De Beers set up a limited operation, mining the richest areas of the main kimberlite for almost a decade before closing it in 1982 when the global diamond industry fell into a deep crisis.

The site sat fallow for almost 20 years. Several companies leased it but couldn’t find a way to make a profit. Political instability in Maseru did not help, especially when it exploded into violence in 1998, which destroyed much of the capital and several surrounding towns.

When peace was restored the following year, the factions formed a unified government, which decided to restart Letseng to get funds flowing into the national treasury. It created the Letseng Diamond Company to acquire the mining lease from the South African gold mining firm that had held it for several years. It took five years to resume small-scale production—less than 40,000 cts per year.

By 2004, Maharasoa had become an executive with the Central Bank of Lesotho, which was working with the government on a deal for Gem Diamonds to acquire a 70% interest in the mine. “The (kimberlite) pipes at the mine were never properly explored, so there was a lot of work to do,” she says. “And even now, (there is) still a lot of work remaining.”

The Lesotho Promise turned up shortly after Gem Diamonds resumed mining operations in 2006. The company sold it for $12.4 million to Safdico, the South African polishing firm majority-owned by London-based jeweler Laurence Graff.

Graff’s cutters spent a year working on the Lesotho Promise. While potentially D-color, it was dappled with black inclusions, making the planning process look more like a battle map, according to a video Graff produced about cutting the diamond.

Twenty-six GIA-graded D-color Flawless diamonds were cut from it, the largest of them a 76.41 ct pear shape graduating down to a 0.55 ct round brilliant. Graff inscribed serial numbers on each of them to indicate their origin. All 26 diamonds were used to design a necklace with a total weight of 223 cts.

	A replica of the Lesotho Promise diamond. Photo by Russell Shor/GIA
By the time Maharasoa joined Letseng in 2009 as CEO, the company had unearthed the 493 ct Letseng Legacy (2007) that Graff/Safdico purchased for $10 million and the 478 ct Light of Letseng (2008), which yielded the 102.79 ct Graff Constellation (2009), which was graded by GIA and according to Graff is the largest known D-Flawless round brilliant diamond.

Shortly after her arrival, the company announced that it had found two colorless diamonds weighing 196 and 184 cts. In September 2014, the company sold a 198 ct potentially D-Flawless diamond at its Antwerp sale for $10.6 million. These finds have helped seal Letseng’s global reputation as a supplier of large, fine diamonds.

Mining here remains challenging, Maharasoa says.

“It is the world’s highest active diamond mine, so the weather is extremely volatile, going down to –25°C in winter,” she says. “We have to maintain our part of the road that not only supplies us with access to and from the mine, but links the town of Mokhotlong to the north of us.”

Supplying the mine with food, fuel and equipment is no small logistical matter, either.

“We use 1.5 million liters of fuel each month, which all has to come by truck,” Maharasoa says. “And then there’s the challenge of getting our 50-ton Caterpillar mining trucks up the mountains to our site.”

Despite these demands, Gem Diamonds has more than doubled the mine’s production in five years to about 100,000 cts a year.

“Letseng has a long life ahead,” Maharasoa says. “We have established a goal that Lesotho’s diamonds, now supplying about 7.5% of our country’s GDP, can achieve 15% within a few years.”

The mining output at Letseng has almost doubled in five years, despite the challenges of mining at 10,000-foot elevations. This mixed production of 204.89 ct goods is but a small portion of production achieved during a five-day mining period. Photo by Robert Weldon/GIA @topic:11


Publish Year: - Title: Diamond: Fun Facts Abstract: April’s birthstone. The hardest natural substance on Earth. More than a billion years old.

There’s a wealth of history and knowledge surrounding diamonds. This popular gem is brilliant, glamorous, breathtaking and mysterious. And you’ll add intriguing to the list after you read through these fun facts about diamonds.
Did You Know?

Diamonds were used to engrave gemstones in India by 300 BCE.
Diamonds can be burned. To burn a diamond, it must be heated to between 1290-1650 degrees Fahrenheit. House fires and jewelers’ torches can sometimes reach that temperature.
D-to-Z color diamonds are the most widely used in jewelry, but diamonds come in all colors of the rainbow. For natural colored diamonds, blue, green, orange and red are the rarest; yellow and brown are the most common.
Diamond weight is measured in carats (not carrots or karats). The word carat is derived from keration, the Greek name for the carob tree whose seed was used for centuries as the standard of weighing precious stones. Because the seed could vary slightly in weight, in 1913, carat weight became metric; one metric carat is equivalent to 0.2 grams or 0.007 ounces.
The largest rough diamond, discovered in 1905, is the Cullinan diamond, weighing in at 3,106 carats (ct.)!

Courtesy of Alan Bronstein and Aurora Gems. Photo: Robert Weldon/GIA
Where do diamonds come from?

Diamonds were formed billions of years ago through a combination of tremendous pressure and temperatures of 1652–2372 degrees Fahrenheit at depths between 90 and 120 miles beneath Earth’s surface.
Diamond crystals are brought closer to the Earth’s surface through volcanic activity.
Diamonds can be found in shallow alluvial deposits where the crystals settle after being transported away from the kimberlite pipes by geologic activity and rivers.
Around 30 percent of the diamonds mined worldwide are gem-quality.
Prior to the 18th century, most diamonds were found in India.
Diamonds were discovered in South America as early as 1725. The discovery occurred in Minas Gerais, Brazil, just as the production in India was dwindling.
Diamonds were found in North America in the 1840s, although this was soon eclipsed by the discovery of diamonds in Africa in the late 1860s and early 1870s and the ensuing Great Diamond Rush.
In 2014, Russia produced the most diamonds by volume and value.
With the opening of the Ekati mine in late 1988, and others in Canada, North America produces almost 10 percent of the total world diamond production by volume.
Even though the U.S. produces almost no diamonds for commercial consumption, America buys more than 40 percent of the world’s gem quality diamonds – making it the world’s largest diamond market.

Now that you know some fun facts about diamonds and where they come from, take a look at some of the most famous diamonds ever found.
The Hope Diamond

Courtesy of Chip Clark, Smithsonian Institution. http://geogallery.si.edu/

The Hope diamond, a Fancy dark grayish blue diamond, fashioned into a cushion brilliant cut, was originally 112 ct. before being cut to its present weight of 45.52 ct.
The Hope diamond is said to be cursed. Although one of its owners, Evalyn McLean believed it to be her good luck charm, her life states otherwise; after possession of the gem, her young son died in a car accident, her husband divorced her and died insane, and her daughter committed suicide.
The Hope diamond, perhaps the world’s most legendary gem, arrived at its present home at the Smithsonian Institution on Nov. 10, 1958 via the U.S. mail – albeit registered first class!

The Uncle Sam Diamond

To date the Uncle Sam, discovered in 1924, is the largest diamond ever found in the U.S.
It was found in the world’s only diamond mine open to the public. The Crater of Diamonds State Park in Arkansas is a dig-for-fee operation for tourists and rock hounds.
Since 1906, more than 70,000 diamonds have been discovered there, including the Uncle Sam diamond, weighing 40.23 ct.

In 2015, a park visitor found an 8.52 ct. diamond at the same park the diamond was discovered.
The Cullinan Diamond

Photo by Peter Macdiarmid/Getty Images

The historic Cullinan diamond, found in South Africa in 1905, weighed an astounding 3,106 ct. It was cut into a total of 105 diamonds of exceptional color and clarity.
The Great Star of Africa (Cullinan I) weighs 530.20 ct. and the Lesser Star of Africa (Cullinan II) weighs 317.40 ct. These two diamonds are part of the crown jewels of Great Britain.
Cullinan III through Cullinan IX, and the remaining 96 diamonds cut from the Cullinan are in private collections.
The two largest stones are mounted in the British crown jewels, while eight others are part of Queen Elizabeth II’s private collection.

The Wittelsbach-Graff Diamond

Photo by Robert Weldon/GIA

The 31.06 ct. Wittelsbach-Graff is one of the largest historic blue diamonds ever fashioned.
Blue diamonds are extremely rare. The presence of boron impurities is often responsible for the color of natural blue diamonds. However, their color can also be caused by radiation exposure or associated with hydrogen. Blue diamonds naturally colored by exposure to radiation are usually described as green-blue, whereas those with color that is associated with hydrogen are described as gray-violet to gray-blue.
The diamond belonged to the Bavarian House of Wittelsbach and was displayed in the Treasury of the Munich Residence until it disappeared in 1931. It was secretly sold in 1951, "rediscovered" in 1961, and then sold again in 1964 to an undisclosed private buyer.
In December 2008, the Wittelsbach-Graff (then called the Wittelsbach Blue) was sold at Christie’s London to jeweler Laurence Graff for just over $24.3 million.
The stone is graded Fancy Deep blue with IF clarity.
Because the Wittelsbach-Graff Diamond and the Hope diamond have similar color and long-lasting phosphorescence – and both are believed to have been mined in India– there has been widespread speculation that they were cut from the same crystal. But were they? Research published in the Summer 2010 issue of Gems & Gemology indicates that the two diamonds do not share a common parent.

Want to learn more? Check out diamond in the GIA Gem Encyclopedia to read more about the history, lore and scientific research surrounding this beloved gemstone. @topic:10