Diamonds & DiamondGrading Synthetics and Treatments19 Table of Contents

Subject Page

Synthetic Diamonds ...... 2 Early Research ...... 3 Success and Progress ...... 3 Applications in Industry and Jewelry ...... 9 Chemical Vapor Deposition ...... 12 Detecting Synthetic Diamonds ...... 13 Detecting CVD Synthetic Diamonds ...... 20 Color Treatments ...... 21 Irradiation ...... 22 Annealing ...... 26 Heat and Pressure ...... 26 Coatings ...... 31 Recognizing Color Modifications ...... 31 Clarity Treatments ...... 34 Laser Drilling ...... 34 Internal Laser Drilling ...... 35 Fracture Filling ...... 35 Detecting Fracture Filling ...... 36 Disclosing Fracture Filling ...... 38 Treated Diamonds and the Marketplace ...... 39 Key Concepts ...... 41 Key Terms ...... 42 ©2002 The Gemological Institute of America All rights reserved: Protected under the Berne Convention. No part of this work may be copied, reproduced, transferred, or transmitted in any form or by any means whatsoever without the express written permission of GIA. ©Printed in the United States. Reprinted 2004 Revised and updated 2008

Cover photos: (clockwise from left) Tino Hammid/GIA, Christie’s Images Inc., John Koivula/GIA, Vincent Cracco/GIA. Back cover: Glodiam Israel Ltd. Facing page: The diamonds in this stunning brooch and earring suite are all natural, but they feature both treated and natural colors. ©1998 Tino Hammid

SYNTHETICS AND TREATMENTS

People have revered the diamond as a precious product of nature for Key Concepts thousands of years. By now, you’ve learned about its progress from Diamond’s beauty, rarity, and value simple carbon atoms to rough diamond to finished gem. You understand how diamond’s rarity gives it exceptional value in the gem world. Is it inspire research into synthesis and any wonder that, through the ages, alchemists and researchers have made treatment. countless attempts to duplicate and enhance diamond’s unique properties and structure? Through careful research, scientists have discovered ways to make natural diamond “better”—to hide its imperfections or to make it a more attractive color. Benvenuto Cellini, the sixteenth-century Italian goldsmith and gem historian, wrote about early gemstone color treatments. He described the heating of sapphire, topaz, amethyst, and other gem minerals in fire until they lost their color—and imitated diamond. Those early searches for diamond look-alikes later developed into searches for techniques to make diamonds. Researchers tried to find just

©2002 GIA. All rights reserved. 1 DIAMONDS AND DIAMOND GRADING 19

the right combination of ingredients, temperature, and pressure that would allow technology to do nature’s work. In the 1950s, scientists began making synthetic diamonds. Now they’re widely used in industry, mostly in cutting instruments and abrasives. A few have been produced for the gem market. In this assignment, you’ll learn about synthetic diamonds and about color and clarity treatments, along with some basic detection skills. Now that synthetics and treatments have become part of the diamond industry, gem professionals who can detect them will be in demand at every level. By the end of this assignment, you’ll have gained valuable knowledge to help you meet that demand.

SYNTHETIC DIAMONDS I When was synthetic diamond first successfully grown? I How do synthetic diamonds fit into industry and the jewelry market? I What are some basic detection methods for synthetic diamonds?

Michael Nicholson/Corbis Sixteenth-century Florentine sculptor As you learned in Assignment 18, there’s an important difference between and goldsmith Benvenuto Cellini wrote synthetic diamonds and simulants. Synthetic diamonds are made in the some of the earliest descriptions of laboratory, and they have essentially the same chemical composition and gemstone treatments. crystal structure as natural diamonds—or at least as close as researchers can make them. Their physical and optical properties are nearly the same as natural diamonds. Simulants, on the other hand, only look like diamonds. They can be natural or made in a lab from a variety of materials, and their chemical compositions and physical and optical properties are different from those of diamond.

Synthetic diamond— Manufactured diamond with essentially the same physical, chemical, and optical properties as natural diamond.

Joseph Schubach Although this manmade material—synthetic moissanite—imitates the look of diamond, it doesn’t share its properties.

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It wasn’t until the development of giant presses, like this one at GE, that scientists were able to create the high levels of heat and pressure needed to synthesize diamonds.

EARLY RESEARCH In 1797, English chemist Smithson Tennant demonstrated that diamond was nothing more than a very dense form of pure carbon. The fact that carbon was plentiful inspired researchers to explore the possibility of turning some of it into much rarer diamond. Through the 1800s and early 1900s, many researchers and chemists tried to create synthetic diamond from a variety of carbon-containing com- pounds. Early technical realities stopped them from making much progress: They knew they needed high levels of heat and pressure for diamond formation, but didn’t have the technology to produce the right conditions.

SUCCESS AND PROGRESS Then, in 1941, Dr. Percy W. Bridgman, an American researcher who specialized in high-pressure physics, came to an agreement with the General Electric Corporation (GE) and other commercial parties. GE assigned

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Hulton-Deutsch Collection/Corbis Percy Williams Bridgman was one of the pioneers of diamond synthesis research.

Bridgman to design a laboratory especially for the production of synthetic diamonds. Before World War II interrupted the project, Bridgman and his colleagues made important advances in high-pressure technology—but no diamonds. In 1951, GE formed another research group to expand on Bridgman’s work. By 1953, they had designed equipment capable of reaching and maintaining extreme pressures and temperatures. After that, the only modifications they made were to the apparatus that actually held and compressed the raw materials. Finally, a belt-type apparatus designed by team member Dr. Tracy Hall succeeded. GE scientists created their first batch of synthetic industrial diamonds in December 1954. After careful testing of the products and successful repetition of the process, they announced the achievement to the world on February 15, 1955.

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Key Concepts Research into diamond synthesis began before 1800, but producers didn’t succeed until the 1950s.

Bettmann/Corbis Although Swedish researchers also succeeded in synthesizing diamonds, GE was the first to document the process. These tiny diamonds represent that first success.

A Swedish electric company—Allmana Svenska Elektriska Aktiebolaget—had actually made diamonds two years earlier. Their scientists started some diamond-making projects in the 1940s, then abandoned them. They began again in the early 1950s. In February 1953, they made several tiny synthetic diamonds. Even better, they were able to repeat their success in May and November of the same year. But the Swedish scientists decided that their method was too difficult, too slow, and too costly to be commercially feasible. They didn’t announce their accomplishment until two years after GE’s success. By then, it was too late for them to be recognized as the first diamond makers. Today, almost all synthetic diamonds are grown using the process developed by the diamond synthesis pioneers. This process is called high- pressure, high-temperature, or HPHT. GE began marketing synthetic diamond grit in late 1957. They kept their process secret for the next two years under federally enforced secrecy regulations. GE filed worldwide patents in 1959, and the team published details of its procedures. De Beers soon followed with their High pressure, high temperature own patent for diamond synthesis. (HPHT)—Diamond synthesis You might think that the step from growing experimental batches of method that mimics the pressure tiny synthetic diamond crystals to creating large, high-quality crystals and temperature conditions that would be a relatively small one. But progress was limited. Larger crystals lead to natural diamond take a lot longer to form than tiny ones. The challenge for researchers formation.

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carbon source

heating anvil element

metal flux high-pressure cell

seed crystal

There’s a container—or high-pressure cell—at the center of the diamond press. Within the cell, carbon atoms are sub- jected to intense heat and pressure. The atoms travel though the growth medium— a metal flux—and crystallize on the seed crystal as synthetic diamond.

Both by Peter Johnston/GIA All diamond presses work on the same principle: extremely high pressures and temperatures applied to the necessary ingredients. This illustration shows the six anvils in a modern diamond press. They’re pushed inward by pistons—that aren’t shown here—and exert enormous pressures on a tiny central container where crystal growth takes place.

was to increase crystal size and, at the same time, control the quality of the crystals. The size of the necessary equipment was also a limiting factor. The GE research team worked on solving these problems and, in 1970, announced the creation of the first cuttable, gem-quality synthetic diamonds. In 1970 and 1971, Lazare Kaplan and Sons of New York cut some of those first gem-quality synthetic diamonds, which weighed about 1 ct. each in rough form. Fashioned stones cut from those crystals ranged from 0.26 ct. to 0.46 ct. in weight, and from F to J in color. There were also some yellows and blues, and the highest clarity was VS. Over the next 14 years, a few synthetic gem-quality diamonds were used for research and for special scientific uses. During this period, re- searchers solved the technical problems preventing large-scale manufacture.

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Robert Weldon/GIA Most synthetic diamonds are small and yellow in color. These specimens—produced in Russia—range from 0.14 ct. to 0.88 ct.

In 1985, Japan’s Sumitomo Electric Industries began commercial produc- tion of large, high-quality synthetic diamonds. Sumitomo produces mostly yellow Type Ib diamonds, which contain isolated nitrogen atoms as trace elements. They add the chemical element boron to provide electrically conductive blue Type IIb diamonds for certain applications. They’ve also been able to produce some Type IIa colorless diamonds. Sumitomo markets its synthetics only for industrial and high-technology applications. The synthetic industrial diamond market is dominated by two of its originators: De Beers and GE. Production consists mostly of synthetic industrial diamond grit. Its superior cutting and polishing abilities make it ideal for use in a variety of tools, including drills, saws, and polishers.

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Lowell Georgia/Corbis

Rob Crandall/Stock Connection/PictureQuest The properties of synthetic and natural diamonds make them ideal for use in industrial cutting tools. They’re embedded into drill bits, machining tools, and saws. They’re also used as scalpels for delicate surgeries, and to engrave fine glassware (facing page).

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Key Concepts Synthetic diamonds are better for many industrial applications than natural diamonds.

APPLICATIONS IN INDUSTRY AND JEWELRY Diamond’s properties of hardness, high thermal conductivity, optical transparency, and high electrical resistance make it uniquely suited for many high-technology applications. Industrial tools embedded with natural or synthetic diamonds are used for machining alloy engine blocks and other automotive components. Some are designed for cutting natural hardwoods, granite, and marble. Scientific advances have made synthetic diamonds better than natural diamonds for many industrial uses. One advantage of synthetics is that manufacturers can control the growth process. Unlike natural diamonds, which nature fashions randomly, synthetics can be turned out in predictable shapes and sizes. Manufacturers can also control impurities and other aspects of quality. In many cases, synthetic diamond grit outlasts natural diamond grit because of its uniformity. Type IIa diamond—natural or synthetic—conducts heat more than five times more efficiently than copper. This high thermal conductivity allows it to take away the heat caused by the friction between moving parts. This makes it possible for a tool to operate under severe conditions without overheating. “Slices” of large single-crystal synthetic diamonds are used

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Synthetic diamonds have many high- tech applications for the electronics and optics industries. Some large, high-quality synthetics are sliced for use as laser windows and heat sinks.

Tino Hammid/GIA GE has produced gem-quality synthetic diamonds for experimental purposes— including some grayish blue and near-colorless stones—but they’ve never offered them for commercial sale.

Key Concepts for industrial and surgical tools, laser windows, and heat sinks, among The use of synthetic diamonds in other things. (A heat sink draws unwanted heat away from an electronic jewelry is limited by high production device.) costs. Because of the extraordinary equipment and energy requirements, most production of large synthetic diamond crystals in the 1990s was for exper- imental and research purposes only. Their presence in the jewelry market was limited by the high expense of producing colorless, cuttable diamonds. Bulk production of larger diamonds was limited because larger crystals take longer to grow.

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Key Concepts Most HPHT synthetic diamonds are yellow or brown because they contain nitrogen impurities.

Shane McClure/GIA Tino Hammid/GIA Most synthetic diamonds are yellow Russian scientists have successfully because it’s difficult to keep nitrogen grown near-colorless synthetic diamonds, out during the growth process. These but the stones have not appeared in three platinum rings contain yellow the commercial gem market in large Russian synthetic diamonds. They range quantities. from 0.30 ct. to 0.40 ct., and are some of the few synthetic diamonds that appear in jewelry.

In 1990, De Beers announced that the largest synthetic diamond grown to date was a 14.20-ct., industrial-quality yellow crystal, which took 500 hours to grow. By 1993, the largest reported crystal weighed 34.80 cts. and took 600 hours—25 days—to reach that size. By 2000, De Beers indicated that it was possible to grow crystals larger than 30 cts. in less time, but only some areas of the manmade crystals were gem quality. In spite of these obstacles, a few companies around the world spent the late 1990s preparing for full production of colorless, gem-quality, marketable cut diamonds. The challenge is that most HPHT synthetic diamonds are either yellow or brown because it’s difficult to keep nitrogen out of the growing crystals. Manufacturers can produce blue diamonds by allowing crystals to grow in the presence of boron. By 1990, GE had grown near-colorless Type IIa diamonds of 1.00 ct. and larger with no detectable nitrogen by using a metal flux. A flux is a solid material that, when melted, dissolves other materials. Special com- pounds added to the flux prevented nitrogen from entering the growing crystal’s structure. De Beers also grew some colorless synthetic diamonds experimentally for industrial applications. GE and De Beers haven’t yet released their experimental diamonds into the gem market. Russian scientists grew near-colorless synthetic diamonds for the gem market, but never reached commercial production levels. However, during the 1990s, small quantities of colored synthetic diamonds reached the gem market, distributed by a Thai-Russian joint venture in Bangkok, Thailand.

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Chemical vapor deposition (CVD)—An industrial process adapted to allow growth of synthetic diamond from carbon- rich gas in thin layers onto a silicon or diamond surface.

Maha Tannous/GIA These synthetic diamonds, with their natural-looking colors, are from Chatham Created Gems.

In the early 2000s, a US company called Gemesis Corporation began manufacturing and selling yellow and orange-yellow HPHT synthetic diamonds for jewelry use. The company is working on techniques to pro- duce colorless synthetic diamonds in commercial quantities. An important supplier of HPHT synthetic diamonds for jewelry is Chatham Created Gems. The company introduced a line of colored syn- thetic diamonds in yellows, blues, pinks, and greens. Their colors are less Maha Tannous/GIA saturated than most colored synthetic diamonds, making them more natural-looking.

CHEMICAL VAPOR DEPOSITION

In 2003, Apollo Diamond Inc., a US manufacturer, announced successful growth of jewelry-size synthetic diamonds by a technique that doesn’t require high pressure and uses relatively modest temperatures of 1346°F James Shigley/GIA to 2066°F (730°C to 1130°C). The method—called chemical vapor depo- In the early 2000s, the Gemesis sition (CVD)—was already in use for many industrial applications, Corporation began synthesizing yellow to including the production of high-purity thin films for semiconductors. orange diamonds for jewelry use (top). Apollo adapted CVD to allow the deposition of synthetic diamond from a Many contain small metallic flux inclu- sions that can help with identification carbon-rich gas onto a silicon or diamond surface. The synthetic diamond (bottom). grows in thin layers, and its final thickness depends on the amount of time allowed for growth.

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Robert Weldon/GIA Advances in CVD synthetic diamond growth have led to production of some attractive gem-quality stones.

Peter Johnston/GIA In the CVD growth process, a microwave beam causes carbon to precipitate out of a plasma cloud and deposit onto a surface of diamond or silicon. As the carbon deposits build, synthetic diamond forms.

At first, the synthetic diamond produced by CVD wasn’t thick enough to yield fashioned stones. The manufacturer has since displayed some fashioned gems over 1 ct. in size.

DETECTING SYNTHETIC DIAMONDS While researchers develop new and better production methods, the main challenges for the jewelry professional are detection and disclosure. A trained gemologist can readily identify most HPHT synthetic diamonds using standard gemological instruments and three basic procedures: • Examining the diamond with a microscope, looking for inclusions, color zoning, and graining • Checking the diamond’s fluorescence under ultraviolet (UV) radiation • Checking the diamond’s reaction to a magnet Synthetic diamonds don’t have the same variety of mineral inclusions that natural ones do. A synthetic diamond won’t contain included minerals Both by John Koivula/GIA like garnet, diopside, or even another diamond. The only inclusions a As they grow, synthetic diamonds synthetic diamond might contain are dark, opaque remnants of the metallic often trap metallic bits of the flux that flux it grew in. surrounds them. The bits become inclusions that are usually opaque and These inclusions need to be examined closely. You can use fiber-optic light highly reflective (top). They occur in a to determine if they’re highly reflective or metallic looking. An inclusion of range of angular shapes, although the metallic flux can be conclusive evidence that the diamond is synthetic. square shape (bottom) is fairly unusual.

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With training and careful observation, The included mineral crystals in natural gemologists can identify most synthetic diamonds are more transparent and diamonds using standard gemological less obvious than the flux in synthetic techniques. In this case, inclusions of diamonds. highly reflective metallic flux indicate this diamond’s manmade origin. (19X)

Natural diamond inclusions like these The transparent, octahedral diamond can resemble the flux in synthetic crystals in this fashioned diamond look diamonds. very different from the metallic dark or shiny flux particles that decorate the inte- riors of many synthetic diamonds.

A synthetic diamond won’t always have inclusions. One of the best ways to distinguish natural from synthetic diamonds is related to how they grow, and to the shape of their crystals. Although a cutter can remove the exterior of a crystal during polishing, crystal growth structures like graining and color zoning remain in the fashioned stone. These features can help you identify the gem as synthetic or natural. As you learned in Assignment 4, diamonds grow deep in the earth, under a range of temperature and pressure conditions. The temperatures for natural diamond crystal growth are higher than those used to grow

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NATURAL DIAMOND SYNTHETIC DIAMOND

seed crystal

A vertical cross section of a synthetic cross section cross section diamond shows its upward and outward growth from the tiny seed crystal. Its characteristic zoned pattern forms when nitrogen atoms, which are present as impurities during crystal growth, are concentrated parallel to certain crystal faces.

Blue fluorescence, concentric Yellow or greenish yellow growth pattern fluorescence, cross-shaped growth pattern

All by Peter Johnston/GIA Natural and synthetic diamonds have different shapes and crystal growth structures. Of the natural diamonds that fluoresce, most show consistent growth in all directions from a central core, so a cross section through a crystal (left) reveals a concentric pattern like the layers of an onion. Synthetic diamonds (right) grow quite differently: A cross section shows strongly zoned growth that creates a cross-shaped fluores- cence pattern.

HPHT synthetic diamonds in the laboratory. At high temperatures, diamonds grow as octahedral crystals, but in the lower temperatures of the laboratory, they grow as crystals with both octahedral and cubic faces. Natural diamond crystals grow relatively equally in all directions from a small central core. Synthetic diamond crystals grow upwards and outwards from a tiny seed crystal that’s placed on a flat surface. This leads to an entirely different crystal shape, which looks like a broad-based, tapered pyramid terminated by a small flat face. This is a shape you’ll never see in a natural diamond.

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Tino Hammid/GIA

These Sumitomo synthetics (left) show the usual mixture of sharp-edged cubic and octahedraI faces. They’re very different from the typical rounded octahedral shapes of natural diamond crystals (above).

John Koivula/GIA This 0.78-ct. synthetic diamond has a flattened base where it grew upward from a seed crystal, which is visible at the center. This feature is typical of synthetics, but it’s never seen in natural diamonds, which grow by building layers from the inside out in all directions.

Because the shapes of natural and synthetic diamond crystals are different, their internal growth patterns also differ dramatically. These growth patterns can be among the most reliable ways to separate natural from synthetic diamond.

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John Koivula/GIA Shane McClure/GIA Even after a synthetic diamond is fashioned, it retains crystal growth structures that Because synthetic diamonds grow in proclaim its origin to the trained gemologist. An example is the surface graining on an iron-based flux, they contain many the table facet of this Sumitomo synthetic. metallic inclusions. Some have so many metallic inclusions that they respond to a magnet.

For example, the growth patterns related to the cubic and octahedral Key Concepts crystal faces of the synthetic diamond can make an hourglass-shaped HPHT synthetic diamonds can be graining pattern. Hourglass graining is often visible with magnification identified by their metallic flux through a fashioned synthetic diamond’s pavilion. Color zoning in synthetic diamonds also follows the stone’s growth patterns. Natural diamonds won’t inclusions, growth structures, and show hourglass-shaped growth zoning. fluorescence. If you can’t find any inclusions, graining, or color zoning, test the diamond’s reaction to UV radiation. This is particularly useful if you need to test an entire parcel of diamonds at the same time. Natural diamonds that fluoresce typically display blue fluorescence under longwave UV, and a weaker, often yellow fluorescence under short- wave UV. Synthetic diamonds usually fluoresce yellow to greenish yellow under both longwave and shortwave UV, and the reaction is usually brighter under shortwave UV. The synthetic diamond’s different crystal growth structures show up as a distinctive cross-shaped pattern to both longwave and shortwave UV. In addition, many synthetic diamonds are phosphorescent: Their fluorescent glow remains for a short time after the UV radiation is turned off. This feature makes it possible to examine several diamonds side by side. It’s unusual for a natural diamond to show phosphorescence. Some synthetic diamonds are attracted to magnets because of the tiny metallic inclusions left behind from the flux metal used for diamond

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C. Welbourn John Koivula/GIA Besides its distinctive blue fluorescence, which is typical of many natural diamonds, this 0.30-ct. fashioned gem (left) shows concentric bands of octahedral growth. By contrast, under longwave UV, this Russian synthetic diamond (right) glows a greenish yellow color and has a distinctive cross-shaped fluorescence that reflects its differ- ent crystal growth pattern.

Nicholas DelRe/GIA

Synthetic diamonds show a variety of fluorescence patterns. Through the crown, you’ll usually see a cross-shaped pattern (left), while from the side, an hourglass pattern (above) is typical.

growth. Although some of the inclusions might be too small to be visible even under a microscope, you can test for their presence by suspending a synthetic diamond on a thread and holding a strong magnet near the stone. The metallic inclusions are attracted to the magnet, so when the magnet moves, the synthetic diamond moves along with it. It’s extremely rare for a natural diamond to have this property. The magnet test isn’t as useful as it once was. For one thing, it’s imprac- tical for mounted or very tiny synthetic diamonds. For another, as technology improves, the quantity of metallic inclusions will decrease.

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James Shigley/GIA Shane McClure/GIA Gemesis synthetic diamonds can be identified by their distinctive colorless zoning (above). They also might feature cloud-like masses of tiny pinpoints (right) that are more scattered than the clouds in natural diamonds.

Gemesis developed its technology to the point where the visual charac- teristics that distinguish its synthetics are generally less obvious than the characteristics of other synthetic diamonds. The cutting process eliminates many of the remaining characteristics. Magnification might reveal color zoning and small opaque or reflective metallic inclusions, but the inclusions are often cloud-like and difficult to distinguish. Metal flux inclusions are often parallel to a rough crystal’s outer surface, or found along boundaries between internal growth sectors. Fluoresence varies more in Gemesis synthetic diamonds than it does in other synthetics. Gemesis synthetics can be inert under both LWUV and SWUV, or they might fluoresce a weak or very weak orange, possibly with a green cross-shaped pattern superimposed over it. The intensity of the SWUV reaction might be either slightly weaker or slightly stronger than the intensity of the LWUV reaction. De Beers researchers developed two diamond-verification instruments in the mid-1990s for use in gemological laboratories: the DiamondSure and the DiamondView. The DiamondSure is a fairly simple instrument that can separate natural from synthetic colorless or near-colorless diamonds based on the way each absorbs light. It works because most natural near-colorless diamonds are Type Ia, so they contain plentiful amounts of nitrogen. When nitrogen is plentiful in diamond, it causes a distinctive—and detectable—absorption pattern. So far, virtually all colorless synthetic diamonds that have been tested are Type IIa. Type IIa diamonds don’t show this distinctive nitrogen absorption pattern. The DiamondSure can test both mounted and unmounted gems. There are a few natural diamonds the DiamondSure can’t identify, but the instru- ment indicates if further testing is needed.

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Key Concepts CVD synthetic diamonds lack the flux metal inclusions that are common in HPHT synthetic diamonds.

Eric Welch/GIA De Beers’ DiamondView relies on the different fluorescence patterns of natural and synthetic diamonds to separate them. The instrument consists of a fluorescence imaging unit, a TV camera, and a specially programmed computer. A trained operator evaluates the stone’s image to determine its origin.

The diamonds that don’t pass the DiamondSure’s test can be positively identified by the DiamondView. It’s a more complex, more expensive instrument that displays a diamond’s crystal growth structure as a pattern of UV fluorescence, which is very different for synthetic diamonds than it is for natural diamonds. It can help to separate natural from synthetic for both near-colorless and colorless diamonds. De Beers created these instruments for research purposes but plans to increase production if gem-quality synthetic diamonds gain a greater presence in the industry.

DETECTING CVD SYNTHETIC DIAMONDS CVD synthetic diamonds are faint brown to dark brown, near-colorless to colorless, or light blue to intense blue. They might contain small, irregu- larly shaped, black inclusions that are probably graphite. The stones lack the flux metal inclusions common in synthetic diamonds grown by high- pressure synthesis. Some CVD synthetic diamonds fluoresce a very weak yellow-orange under LWUV, and a weak to moderate yellow-orange under SWUV. Others are inert. Advanced testing reveals distinctive features in the absorption spectra of these synthetic diamonds that separate them from other synthetic diamonds and—more importantly—from natural diamonds. The presence of synthetic diamonds in the marketplace will challenge dealers and consumers to be more careful about diamonds in general. Of course, disclosure should be the rule at every step of a synthetic diamond’s journey through the market, as well as during an appraisal. But you might not always be told that a diamond is synthetic. Whenever you come across a diamond you think might be synthetic, examine it carefully, and consider sending it to a gemological laboratory for further testing.

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Creative marketing of naturally colored diamonds in the 1980s and 1990s helped increase public awareness and demand for these rare natural treasures.

©1998 Tino Hammid These diamonds are natural, but they owe their beautiful colors to laboratory treatments.

COLOR TREATMENTS I What factors encouraged development of diamond color treatments? I How does heat affect treated diamond color? I How did a modern color-modification process evolve from diamond synthesis? I What are some clues for detecting color treatments?

Even though most people think of diamonds as colorless, colored diamonds are more popular than ever. Promotion of pink and brown diamonds from Australia’s Argyle mine has probably done more to increase public awareness of colored diamonds than any other factor. Increased interest has led to new research into the causes of natural diamond color.

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Irradiation—Exposure of a material As you learned in Assignment 12, diamond color comes from the to radiation; causes color change presence of impurities or the effect of distortions or defects in a diamond’s in diamonds. crystal lattice. Diamonds tend to be yellow when nitrogen is present as an impurity and blue when the impurity agent is boron. Green diamonds get Linear accelerator—A machine their color when radiation displaces atoms from their normal positions in used to accelerate electrons to the crystal lattice. And the color in pink and brown diamonds is due to high energy along a straight path. graining, an irregularity or defect in the crystal that occurs during growth. While studying the causes of natural color, scientists began to under- stand how some of those color-causing conditions might be reproduced in the lab. Since then, scientists have experimented with many ways to change or modify diamond color. The value and rarity of naturally colored diamonds have inspired many struggles to create their colors in the lab.

IRRADIATION Natural radiation in the ground makes the diamonds near it turn green. In the early 1900s, Sir William Crookes tried to duplicate nature’s process and manufacture green diamonds in the laboratory. Crookes’ experiments marked early research into color-treating diamonds by artificial irradia- tion. He found that he could make diamonds turn green by burying them in a radium compound for up to a year. Unfortunately, the treatment also made the diamonds highly radioactive. Atomic science researchers invented the cyclotron soon after World War II for nuclear research. It was a large machine that accelerated atomic particles around a circular path. Its introduction encouraged major developments in irradiation, and made artificial irradiation of

Robert Weldon/GIA All green diamonds get their color from exposure to radiation, whether natural or lab- created. This 3.06-ct. diamond’s color treatment was disclosed, but the laboratory process is so similar to natural irradiation that it would be otherwise impossible to prove the origin of its color.

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Bettmann/Corbis Roger Ressmeyer/Corbis The first irradiated diamonds were treated in a cyclotron, a large device developed for atomic research (above). Today, most diamond treaters use more compact equipment, like a linear accelerator (right).

diamonds in commercial quantities possible. But this treatment resulted Half-life—The length of time in only shallow penetration of the atomic particles into the diamond, so required for half of a group of it caused distinctive color zones. atoms of a particular type (radioactive) to decay into Later in the 1900s, researchers developed the linear accelerator. It another type (non-radioactive). also accelerates atomic particles, but along a straight path rather than a circular one. Today, penetration with high-energy electrons in a linear accelerator is one of two frequently used irradiation techniques. Depending on the material and treatment conditions, this process usually produces blue or blue-green colors. The other technique involves bombardment with neutrons, usually in a nuclear reactor. Diamonds treated this way usually become green, blue-green, or dark green. Both of these modern processes produce uniform color without zoning Key Concepts because the electrons and neutrons penetrate very deeply. And the Modern diamond irradiation methods radioactive atoms in diamonds treated with either process usually have leave little or no color zoning and no short half-lives, so the diamonds lose their radioactivity before they’re radioactivity. released into the market.

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After one half-life, half of the radioactivity remains.

one half-life

four half-lives

six half-lives

ten half-lives After ten half-lives, only one thousandth of the radioactivity remains.

Peter Johnston/GIA Half-life is a measure of the time it takes for half of the radioactivity in an object to break down. It can be shorter than a second or as long as billions of years, depending on the radioactive material. When each half-life ends, another begins.

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RadeLukovic/iStockPhoto The most common, and least expensive, radiation detector is a Geiger counter. It converts radioactive waves to electrical pulses that trigger audible clicks. It’s a valuable tool to have on hand, especially if you deal in estate jewelry, which is more likely to contain potentially hazardous diamonds treated with radium salts.

Robert Weldon/GIA Whether irradiated in a laboratory—like these two examples—or in the earth, green diamonds can be very attractive.

Scientists use half-life to measure the long period of radioactivity in a material. They define a half-life as the amount of time required for half the radioactive atoms of a substance to become non-radioactive. Once the first half decays in this way, the “clock” resets and half of what’s left begins to decay. Then half of that must decay. This process continues until half of what’s left is an undetectable amount. A half-life can vary from less than a second to billions of years. The Geiger counter is a fairly simple and affordable instrument that can detect and measure moderate to high levels of radioactivity. At the other end of the scale are complex instruments used by research labs.

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Many countries have government agencies that regulate the amount of radioactivity allowed in gemstones. In the US, the Nuclear Regulatory Commission (NRC) regulates manmade radioactivity. At one time, their regulations applied only to gems irradiated in a reactor. A law that passed in 2005 and took effect in 2007 extended their control to gems irradiated in accelerators, which includes most irradiated diamonds. The Commission allows radioactive gemstones to be released to the public only after they’re tested by an NRC-licensed organization. The testing organization can assign a release date to a radioactive gem, depending on when the radioactivity is expected to be at a safe level. After the initial release, they can be resold without limit. Shane McClure/GIA Sometimes, the release date is far in the future. Some gems irradiated This 0.55-ct. synthetic diamond was in the early to mid-1900s are still radioactive. originally brownish. A combination of irradiation and heating turned it an Color-modifying irradiation treatment usually comes after a diamond attractive red. is cut and polished. Unfortunately, irradiated colors are sensitive to heat. Technicians use cold running water to prevent color changes during the irradiation process, which generates a lot of heat. After the gem is set, the heat from jewelry repairs, recutting, or repolishing might also change its color.

ANNEALING Key Concepts A controlled heating and cooling process called annealing, which you Heat can alter irradiated colors. read about in Assignment 12, is another way to change diamond color. When it follows irradiation in a two-step process, annealing modifies Annealed diamond color can change irradiated colors to produce brown, orange, or yellow. Rarely, it can also produce shades of pink, red, or purple. In the 1970s, many diamond colors if it’s exposed to heat during routine were modified this way. repairs. Annealing is also sometimes used alone. The process changes diamond colors in a series—generally blue to green to brown to yellow—and the treatment is stopped when the desired color is reached. In the early 1990s, treaters discovered it was possible to treat typical yellow to brown synthetic diamonds to produce more marketable reddish colors. As with irradiation, if heat is later applied to an annealed diamond during routine repairs, it can drastically alter its color.

HEAT AND PRESSURE In the late 1990s, advances in diamond synthesis led scientists to experiment with ways to modify diamond color using the same HPHT equipment. Those experiments resulted in two different processes. One process improves the color of brownish Type IIa diamonds, making them almost colorless. The other creates green or yellowish green diamonds from brown Type Ia ones. After HPHT processes were developed for commercial use, the GIA Laboratory and other gemological labs explored ways to detect their presence.

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Both by Phillip Hitz/Gübelin Gem Lab HPHT processing can dramatically improve a diamond’s color. Before processing, these Type IIa diamonds ranged from N-color to Fancy Light brown (top). After processing by GE, their color improved significantly, and they received color grades of D to H (bottom).

To produce or remove diamond color, HPHT processors use essentially the same equipment as manufacturers of synthetic diamonds. Presses like this one produce extremely high pressures and temperatures.

GE—the same company that pioneered diamond synthesis—selected Type IIa diamonds for HPHT processing. Type IIa diamonds are very rare in nature: They make up less than 1 percent of diamonds mined. They have a very pure chemical composition, and only very small amounts of nitrogen or boron. Some very large diamonds—including the 530.20-ct. Cullinan I—are Type IIa. Shortwave UV radiation passes through Type IIa diamonds and not through other types, so gemologists can take advantage of this property to separate them.

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The Deepdene: Treated, and Treated Again

Christie’s Images Inc. Christie’s auction house sold the Deepdene diamond in 1997, set in a beautiful cultured pearl and diamond choker necklace.

THE DEEPDENE Weight: 104.88 cts., then 104.52 cts. Cut: Cushion Color: Light yellow to deep green to golden yellow (treated color)

The Deepdene is probably the most famous color-treated diamond in existence. Gem historians believe that it came from a South African mine in 1890 and that it was originally cut by the I.J. Asscher Co. in Amsterdam. It appeared on the market as a light yellow, cushion- shaped, 104.88-ct. diamond. Its first known owner was famed New York diamond dealer Lazare Kaplan.

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In the early 1900s, Helena Bok, a Pennsylvania socialite, bought the diamond. She named it Deepdene, which means “deep valley” in old English, to honor her family’s estate. The Bok family loaned it to the Philadelphia Academy of Sciences, which dis- played it publicly in the 1940s. The family sold the diamond to Harry Winston in 1954, and Winston sold it the following year. Sometime after that, the Deepdene was irradiated in a cyclotron, which turned it a hand- some green color. The treaters recut the culet and pavilion Christie’s Images Inc. slightly to eliminate the umbrella- In 1997, Christie’s photographed the shaped color zoning left by the Deepdene diamond out of its setting. radiation treatment. That’s when This side view shows its lovely treated its weight changed to 104.52 cts. yellow color. The diamond was sold again in 1971. By that time, the Deepdene was yellow again. When questions arose about the origin of its color, gemological expert Dr. Eduard Gübelin stepped for- ward. He said that he had examined the diamond and determined that it was annealed. It’s said that Dr. Gübelin also sent the diamond to Robert Crowningshield at GIA, who agreed that its yellow color was the result of heat treatment. In November 1997, the Geneva branch of Christie’s auction house sold the Deepdene at auction. GIA Laboratory had examined it a few months earlier and pronounced it VS1 clarity. This time, the gem was surrounded by four rows of cultured pearls and diamonds in a magnificent choker necklace. The winning bid was $647,482. Because of its color and weight changes, there was some contro- versy over whether the modern diamond was indeed the original Deepdene. Experts solved the mystery by obtaining a photograph of the original gem from Helena Bok. They compared the photograph to the actual diamond under a special microscope that magnified them both 12.5 times and displayed the images side by side. The proof was an identical natural, just above the girdle. It convinced researchers that they held the original Deepdene diamond.

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Both by John Koivula/GIA After HPHT processing, some cleavages take on a granular, In some HPHT diamonds, solid inclusions surrounded by reflective appearance. stress cracks display a black inner area of graphite and a brighter halo of outwardly radiating cracks. (40X)

Key Concepts Most Type IIa diamonds have very few clarity characteristics beyond HPHT eliminates the structural small fractures and tiny mineral inclusions. Many have clarity grades of distortions that cause brownish VVS or better, and HPHT processing doesn’t significantly affect most inclusions or clarity grades. GE selects diamonds with the highest possible coloring in some Type IIa diamonds. clarity for processing. As you learned in Assignment 12, some Type IIa diamonds are brown. HPHT can dramatically improve The brown color is caused by internal, parallel grain lines, which are actu- the color and value of brownish ally distortions of the diamond’s crystal structure. These are the diamonds diamonds. that GE processes with HPHT. High pressures and temperatures eliminate the brown color by reducing or removing these structural irregularities. The first commercial release of HPHT diamonds occurred in March 1999. The release was the result of a partnership between GE and major diamond manufacturer Lazare Kaplan International (LKI). The companies declared that the gems had been processed to improve color, brightness, and brilliance and that the results were permanent and also irreversible. Graphitization—Graphite forma- At first, the stones were known as GE-POL or “Pegasus” diamonds tion around a diamond’s mineral because they were marketed through Lazare Kaplan’s subsidiary, Pegasus inclusions and feathers that Overseas Limited (POL). At present, they’re sold by LKI under the brand results from the extreme condi- name “Bellataire.” tions of HPHT processing. GE and Lazare Kaplan cooperated with GIA and other leading gem labs to help identify defining characteristics for the processed diamonds. They supplied samples of diamonds both before and after processing for the labs to compare and analyze. High temperatures and pressures are risky for some diamonds. Some might break from thermal shock, while others might become chipped or fractured. An effect that can help you recognize them is graphitization, which is the formation of graphite around the diamond’s mineral inclu- sions and feathers.

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Darren Rosario John Koivula/GIA The Bellataire inscription on this diamond identifies it as one High pressures and temperatures can result in the formation that has undergone HPHT processing. of graphite around a diamond’s mineral inclusions. (40X)

Most diamonds need repolishing after HPHT processing, but the improvement in color and value can be dramatic. Brown diamonds of N to O color, and even Fancy Light brown diamonds, can attain D to H grades after HPHT processing. Other manufacturers use similar processes to alter diamond color. They’ve been able to produce intense yellow to greenish yellow stones from brownish Type Ia diamonds. Many diamonds that were modified this way by Russian producers entered the market in 1996.

COATINGS Coatings were one of the earliest methods of diamond color modification, but they fell out of use when more advanced techniques like HPHT emerged. This changed in recent years with the introduction of a new coating method developed and marketed by Serenity Technologies. Jessica Arditi and Jian Xin (Jae) Liao These modern silica coatings are applied to polished colorless or near- A new coating technique can produce a variety of colors on polished diamonds. colorless diamonds. The process results in a variety of natural-looking These stones range from 0.01 to 0.70 ct. fancy colors, including pinks, oranges, yellows, blues, and violets. These coatings are fairly durable, but not permanent. They can be dam- aged by the heat and chemicals used during jewelry repairs and polishing. They also scratch fairly easily. This means that detection and disclosure are vital when handling coated color-treated diamonds.

RECOGNIZING COLOR MODIFICATIONS Most color treatments are difficult to detect. It’s best to send diamonds you suspect of being treated to a gemological laboratory, because sophis- ticated laboratory equipment provides the most reliable origin-of-color identifications. A spectrophotometer, for example, is a complex and

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Both by Phillip Hitz/Gübelin Gem Lab Before HPHT processing, this pear-shaped diamond’s color was Fancy Light brown (left). After processing (right), the diamond received a color grade of D.

Shane Elen/GIA After HPHT processing, this diamond’s surface displayed etching and pitting. This stone will require repolishing before it can be sold. (10X)

Both by Maha Tannous/GIA Some of these brown diamond crystals (above) turned a more desirable greenish yel- low (left) after HPHT processing.

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Key Concepts Most origin-of-color tests should be done by a gemological laboratory.

Shane McClure/GIA Vincent Cracco/GIA Irradiation and heating resulted in the distinct color zone at this diamond’s culet (left). Irradiation can also result in uneven distribution of color, as seen in the pink and yellow zones in this 0.43-ct. diamond (right). expensive instrument that reads a gem’s light absorption across the visible, UV, and infrared ranges. Experienced technicians can interpret that information and usually turn it into an origin-of-color judgment.

There are some clues to color treatments that you can detect under magnification, with fairly simple equipment. As you’ve learned, color zoning parallel to facet junctions is one sign of a cyclotron-irradiated diamond. If a brilliant cut is irradiated from the pavilion, the color zone is an umbrella-shaped area around the culet. If it was treated from the crown, the zone is a dark-colored ring just inside the girdle. You’ll see it if you place the stone on a white surface and look at it through the pavilion. If you see either type of color zoning, you should send the diamond to a gemological laboratory for further testing.

Whether green diamonds came by their color naturally or artificially is Since this is a rough crystal, it’s easy to almost impossible to determine, even with sophisticated laboratory tests. assume that its green color is natural, That’s because all green diamonds are irradiated. Some are irradiated but rough can also be irradiated in the naturally in the earth, and some by scientists in the lab. laboratory.

Identifying HPHT-processed diamonds involves specialized laboratory techniques like spectroscopy and photoluminescence. But it might be possible to detect some signs of HPHT processing with microscope examination. Those signs include damage caused by the extreme heat and pressure conditions, like etched or frosted naturals and fractures that appear frosted or that converted to graphite. You’ll see graphitization in the form of darkened areas in fractures and around feathers.

You can often recognize the signs of color coatings with simple 10X magnification. You’ll often see scratches and other surface features, such as areas with uncoated spots or patches. Looking through the table can make it easier to see these features on the pavilion. Coating irregularities can make a diamond look like it needs cleaning, but they won’t wipe off with the gemcloth.

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CLARITY TREATMENTS I How can laser drilling improve a diamond’s marketability? I What are some benefits and disadvantages of fracture filling? I What is the flash effect?

Very few diamonds are perfect when they come out of the ground. As you’ve learned, some clarity characteristics can be cut away during the manufacturing process. And some can be positioned within the finished diamond so they don’t detract from its appearance or durability. But some require more than that. The late 1900s brought many advances in diamond clarity treatments.

LASER DRILLING Since the early 1970s, diamond manufacturers have used lasers to drill tiny tunnels—thinner than a human hair—into diamonds to reach dark inclusions. The process uses a carbon dioxide laser to heat a tiny area of Before laser drilling, dark included crystals stand out in high relief against the diamond until it evaporates, producing a tiny tube that the operator can the rest of the diamond (top). After the direct toward an unsightly inclusion. diamond is laser drilled and the crystals The laser drill-hole makes it possible to vaporize the inclusion with the are bleached with acid, they’re much less obvious (bottom). laser, bleach it, or etch it out with acid. This lightens a dark inclusion, which can make the diamond more marketable. Laser drilling—Using a concen- In spite of the fact that it disguises an existing inclusion, laser drilling trated beam of laser light to reach often doesn’t improve the clarity grade. In fact, the drill-hole itself a diamond’s dark inclusions and becomes a clarity characteristic. The drill-hole shouldn’t cause a durability disguise or eliminate them. problem, but if it fills with foreign material, it becomes more visible. You might be able to detect a laser drill-hole with careful examination under 10X magnification, but higher magnification is often necessary. You can distinguish laser drill-holes from etch channels—natural, hollow, tube- Key Concepts like features present in some diamonds—by the fact that laser drill-holes Laser drilling can make a diamond are circular in cross section, while etch channels are square, triangular, or more marketable by improving its hexagonal. appearance.

Because laser drill-holes are permanent, gem labs report them as clarity characteristics.

Fracture filling makes a diamond’s fractures less reflective by using a Vincent Cracco/GIA high-RI glass filler. In this close-up of a laser-drilled diamond, Some diamonds contain natural features you can clearly see the drill-hole between called etch channels, which are angular the surface and the inclusion, which was and can display growth marks. By con- Fracture filling is the most common bleached to be less visible. (63X) trast, laser drill-holes are cylindrical and lack any features resembling growth diamond treatment. marks.

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It’s difficult to see a laser drill-hole if it’s very short or covered by a prong in a setting. Once drilled, the hole is a permanent characteristic of the diamond, so all major gem labs grade laser-drilled stones and report the drill-hole as a clarity characteristic. At one time, some industry professionals considered laser drilling a part of the cutting process, and didn’t think it required any special disclosure or description. But now, there’s industry-wide agreement that laser-drilled diamonds should be clearly disclosed all the way from wholesaler to consumer. Vincent Cracco/GIA Internal laser drilling resulted in the unnatural, irregular, wormhole-like chan- nels in this diamond. (63X) INTERNAL LASER DRILLING A variation on laser drilling is called internal laser drilling (ILD). It’s a Internal laser drilling (ILD)—A technique that uses a laser to expand an existing cleavage or create a new clarity treatment that uses a laser cleavage between an inclusion and the surface. This allows the introduction to expand an existing cleavage or of a bleaching solution. The result is the lightening of a dark inclusion, create a new one, allowing the making it less visible. introduction of a bleaching solution. The cleavage created by this procedure is more natural-looking than a traditional laser drill-hole. When you examine a diamond treated with ILD under the microscope, you’ll see a step-like series of tiny cleavages. These wormhole-like channels are definite signs of ILD treatment.

FRACTURE FILLING The first fracture filling treatment for diamonds was introduced in the 1980s. Since then, many manufacturers of filling materials have emerged. The exact composition of the fillers varies from manufacturer to manu- facturer, but they’re all based on the same idea: A molten glass substance is infused into a diamond’s fractures. As you learned in Assignment 8, the refractive index (RI) of diamond makes light behave in a predictable way. When a diamond has a fracture that reaches the surface, the air in the fracture (with its lower RI) inter- rupts light’s path through the diamond and makes the fracture reflective and easier to see. The filling’s RI is closer to diamond’s than to the RI of the air it replaces, so it makes the filled fracture almost invisible to the casual observer. Fracture filling has become a fact of life in the diamond industry— many more diamonds are subjected to this treatment than to irradiation, coating, heating, or pressure. Diamonds that once were considered unsuit- Both by Vincent Cracco/GIA able for gem use can now be treated and made attractive and affordable to The white feathers in this 1.39-ct. Fancy a wider range of consumers. Intense pink emerald-cut diamond (top) detracted from the stone’s color. After Those who never thought they could afford a diamond over a carat the diamond was fracture filled (bottom), suddenly find they can own a larger fracture-filled diamond. This is also most of the feathers became transparent, an advantage to the affluent customer who is looking for a “fun” diamond— and the stone revealed a more highly one that’s flashy but not necessarily expensive. Fracture filling might also saturated pink color. benefit a customer who accidentally cracks a diamond and is looking for a way to make that diamond look almost new again.

35 DIAMONDS AND DIAMOND GRADING 19

Both by Shane McClure/GIA Before treatment (left), this 0.20-ct. diamond’s fractures are large, reflective, and obvious. After fracture filling (right), the same diamond is more attractive. The filler refracts light almost as well as the surrounding diamond, so the fractures are less apparent.

Diamonds as small as melee have been filled, but because of the cost of the treatment, most filled diamonds are over one carat. This is because the marketability of larger stones takes a higher leap with an improvement in apparent clarity. Fracture filling has its advantages—it makes a diamond look better— but it also has some disadvantages. For one thing, the filler sometimes lowers a diamond’s color slightly. Fracture filling can last for years with proper care, but it’s important to know that the fillers can sometimes be damaged by common jewelry repair procedures. Damaging conditions include the high temperatures created during recutting or repolishing and the torch heat generated during retipping or repair. Over time, repeated cleaning can also harm fillers, John Koivula/GIA especially when the method involves steam, acid, or ultrasonics. Prolonged Jewelry repair procedures can damage exposure to UV radiation—even sunlight—can discolor a filler and make diamond fillers. The heat from a jeweler’s torch caused tiny beads of melted filler it look cloudy over time. to leak out of this diamond’s fracture. Some damage is reversible, some is not. It’s possible to replace the filler (50X) if it melts and leaks out, but if it turns dark, there’s no way to make it color- less again. The only solution is to remove it and replace it with new filler. Many major manufacturers of fracture fillings offer lifetime guarantees on their treatments for just this reason. But those assurances of quality are not enough for everyone. While some jewelry stores carry a selection of filled diamonds, others refuse to accept them from their suppliers.

DETECTING FRACTURE FILLING The ability to identify filled diamonds is always essential. It’s important if you have to take jewelry in for repair because everyday repair and cleaning procedures can damage treated stones. And it’s obviously important when you buy or sell diamond jewelry. Your firm’s reputation suffers if you sell a fracture-filled diamond without disclosing the treatment. This

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Key Concepts Some signs of fracture filling are the flash effect, trapped bubbles, and a crackled texture.

Vincent Cracco/GIA This diamond has multiple laser drill-holes and a pinkish purple flash effect that shows it’s also fracture-filled. (37X)

Both by John Koivula/GIA This diamond’s fracture wasn’t completely filled, so it contains large bubbles of In some fracture-filled diamonds, the filler trapped gas. This is one of the features to look for when you suspect the presence has a crackled texture. It’s very obvious of fracture filling. (35X) when the filled fracture is fairly thick. is true even if you didn’t know about the treatment. In extreme cases, nondisclosure can leave you open to a possible lawsuit. As you learned in Assignment 10, the most obvious evidence of fracture filling is called the flash effect, which is a flash of changing color that shows up with proper lighting under magnification. The flash effect results because glass fillers don’t precisely match diamond’s RI for all wavelengths of light. To see it, you must look parallel to the fracture and rock the diamond back and forth. Other signs of fracture filling include gas bubbles trapped in the fracture or in the filler itself. The injected filler can also have a crackled texture. When you see these features under magnification, it’s obvious that they’re not part of the diamond’s original internal structure.

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Key Concepts A few things can make detection a little more difficult. One small filled Disclosure of fracture filling is an fracture is more difficult to see than several, and requires more careful industry requirement. examination. If the filled fracture is in a less-visible part of the diamond, detection is even more of a challenge. Always make sure you examine the diamond from many different angles. Fiber-optic illumination makes the flash effect more evident. Because fracture fillings can be semi-permanent, most gemological laboratories, including the GIA Laboratory, don’t grade filled diamonds. They do, however, report the presence of fracture filling. Its only function is to make a diamond more marketable by disguising its inclusions. If you’re ever unsure about the presence of fracture filling in a diamond, send it to a gemological laboratory for identification. Your reputation could depend on proper identification and disclosure of this or any other treatment.

DISCLOSING FRACTURE FILLING Since its introduction, the industry has debated methods of disclosing fracture filling without alarming the customer. An early solution was the term “clarity enhancement,” which had a more positive sound than “fracture filling.” But the US Federal Trade Commission and others in the industry consider the words “clarity enhancement” misleading. It was soon followed by the term “clarity treatment,” which was adopted by many industry professionals as the preferred—and more correct—term. International diamond professionals and regulatory agencies demand disclosure of fracture filling every time a diamond changes hands. You must tell your clients that they’re buying a fracture-filled diamond and inform them of its special care requirements. They must also understand

Nicholas DelRe/GIA It’s always important to be aware of the presence of fracture filling because ordinary jewelry repair procedures can damage the filler. This 3.02-ct. diamond was mounted in a ring. During the repair process, the heat from the jeweler’s torch darkened the filling and dramatically affected the diamond’s appearance.

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how to inform anyone else who might handle their diamond in the future. That way, they can avoid the damage that’s sometimes associated with the repair or cleaning of fracture-filled diamonds. The issue of the disclosure of fracture filling came to the public’s atten- tion in 1993 when a televised consumer program exposed some jewelers who were selling undisclosed fracture-filled diamonds. The shocking news set the trade buzzing, not only in the city where the deception occurred, but all over the US. Since then, consumers have become better informed about diamond treatments. Many manufacturers of diamond fillers have prepared informative videos and printed materials to help with treatment disclosure. The videos serve a dual purpose. Besides educating customers, they also teach retailers and suppliers about this technology.

TREATED DIAMONDS AND THE MARKETPLACE In the last 10 years, diamond treatments have become much more of an issue in the jewelry trade. As modern clarity and color treatment techniques make many diamonds more marketable, the need for positive, ethical disclosure grows. Most gem professionals, in an effort to preserve their customers’ trust, have been much more careful about detecting and disclosing treatments of all kinds. There are far more treated diamonds in the marketplace than there are synthetic diamonds. Although synthetic diamonds are grown widely for industrial uses, it’s still too costly and time consuming to produce synthetic diamonds on a wide scale for use in jewelry. Even so, it’s important to stay aware of the possibility that a few synthetics might exist in the marketplace.

In 1993, a US television news program exposed jewelers who were selling fracture- filled diamonds without disclosure. The uproar that followed made consumers more aware of treated diamonds in the marketplace.

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Tino Hammid/GIA Even the most expensive jewelry might be set with treated diamonds. This piece, which was offered at a high-end auction, contains a large irradiated brown pear- shaped diamond.

Because diamond treatments and synthetic diamonds are already part of the industry, it’s important for you to learn as much as you can about them. Stay up to date by reading trade journals, and refer to GIA’s Gems & Gemology for the latest scientific news and detection techniques. And always remember that disclosure is not only ethical, it’s good for business.

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Key Concepts Diamond’s beauty, rarity, and value inspire research into Annealed diamond color can change if it’s exposed to heat synthesis and treatment. during routine repairs.

Research into diamond synthesis began before 1800, but HPHT eliminates the structural distortions that cause brownish producers didn’t succeed until the 1950s. coloring in some Type IIa diamonds.

Synthetic diamonds are better for many industrial applications HPHT can dramatically improve the color and value of than natural diamonds. brownish diamonds.

The use of synthetic diamonds in jewelry is limited by high Most origin-of-color tests should be done by a gemological production costs. laboratory.

Most HPHT synthetic diamonds are yellow or brown because Laser drilling can make a diamond more marketable by they contain nitrogen impurities. improving its appearance.

HPHT synthetic diamonds can be identified by their metallic Because laser drill-holes are permanent, gem labs report flux inclusions, growth structures, and fluorescence. them as clarity characteristics.

CVD synthetic diamonds lack the flux metal inclusions that Fracture filling makes a diamond’s fractures less reflective by are common in HPHT synthetic diamonds. using a high-RI glass filler.

Modern diamond irradiation methods leave little or no color Fracture filling is the most common diamond treatment. zoning and no radioactivity. Some signs of fracture filling are the flash effect, trapped Heat can alter irradiated colors. bubbles, and a crackled texture.

Disclosure of fracture filling is an industry requirement.

41 DIAMONDS AND DIAMOND GRADING 19

Key Terms

Chemical vapor deposition (CVD)—An industrial Internal laser drilling (ILD)—A clarity treatment that process adapted to allow growth of synthetic uses a laser to expand an existing cleavage or diamond from carbon-rich gas in thin layers onto a create a new one, allowing the introduction of a silicon or diamond surface. bleaching solution.

Graphitization—Graphite formation around a Irradiation—Exposure of a material to radiation; diamond’s mineral inclusions and feathers that causes color change in diamonds. results from the extreme conditions of HPHT processing. Laser drilling—Using a concentrated beam of laser light to reach a diamond’s dark inclusions and Half-life—The length of time required for half of a disguise or eliminate them. group of atoms of a particular type (radioactive) to decay into another type (non-radioactive). Linear accelerator—A machine used to accelerate electrons to high energy along a straight path. High pressure, high temperature (HPHT)— Diamond synthesis method that mimics the Synthetic diamond—Manufactured diamond with pressure and temperature conditions that lead to essentially the same physical, chemical, and optical natural diamond formation. properties as natural diamond.

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ASSIGNMENT 19

QUESTIONNAIRE

Each of the questions or incomplete statements below is followed by several possible answers. Choose the ONE that BEST answers the question or completes the statement. Then place the letter (A, B, C, or D) corresponding to your answer in the blank at the left of the question. If you’re unsure about any question, go back, review the assignment, and find the correct answer. When you’ve answered all the questions, transfer your answers to the answer sheet.

______1. Synthetic diamond is a A. natural material that looks like diamond. B. manmade material that looks like diamond. C. manmade material with essentially the same physical, chemical, and optical properties as natural diamond. D. manmade material made primarily of carbon forming in a different crystal system than natural diamond.

______2. The use of synthetic diamonds in jewelry A. is limited by high production costs. B. makes up a substantial portion of the market. C. is limited to fancy-colored melee, which is mostly synthetic. D. is currently impossible because the synthetics are too highly included.

______3. Most synthetic gem-quality diamonds are A. blue. B. pink. C. colorless. D. yellow or brown.

______4. Which one of the following clarity characteristics might be found in a synthetic diamond? A. Xenocryst B. Metallic flux C. Garnet crystal D. Diopside crystal

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IF YOU NEED HELP: Contact your instructor through the GIA Virtual Campus, or call 800-421-7250 toll-free in the US and Canada, or 760-603-4000; after hours you can leave a message.

43 DIAMONDS AND DIAMOND GRADING 19

______5. Which one of the following is typical of the UV fluorescence of synthetic diamonds? A. Strong blue under both longwave and shortwave. B. Blue under longwave and weak yellow under shortwave. C. Strong yellow under longwave and none under shortwave. D. Yellow to greenish yellow under both longwave and shortwave.

______6. Which one of the following is used today to safely color-treat diamonds? A. X-rays B. Radium compound C. Ultraviolet radiation D. High-energy electrons in a linear accelerator

______7. GIA Laboratory and other gemological laboratories A. don’t grade fracture-filled diamonds. B. grade diamonds before they fracture fill them. C. only treat diamonds with eye-visible feathers. D. give fracture-filled diamonds grades that are one grade lower than they appear to be.

______8. Annealing irradiated diamonds can produce A. intense blue. B. emerald green. C. D-grade colorless. D. brown, orange, or yellow.

______9. Annealed diamond color can change if it’s exposed to A. ultraviolet rays in sunlight. B. heat during routine repairs. C. chlorine in swimming pools. D. ammonia in cleaning solutions.

______10. The origin of a diamond’s color A. can be determined using a DiamondSure. B. cannot be determined for most diamonds. C. should usually be determined by a gemological laboratory. D. can be easily determined with standard gemological equipment.

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44 SYNTHETICS AND TREATMENTS

______11. Scientists succeeded in producing synthetic industrial diamonds for the first time in the A. 1800s. B. 1940s. C. 1950s. D. 1990s.

______12. Which one of the following is an indication of the HPHT process? A. Flash effect B. Hourglass graining C. Etched or frosted naturals D. Color zoning parallel to facet junctions

______13. Laser drill-holes A. usually reduce the clarity grade. B. don’t need to be disclosed to customers. C. become permanent clarity characteristics. D. aren’t permanent, so major labs won’t grade them.

______14. Color-treating diamonds in a linear accelerator produces A. distinctive color zoning. B. blue or blue-green colors. C. usually green or dark green colors. D. only shallow penetration of the color.

______15. The flash effect proves that a diamond A. is coated. B. is irradiated. C. is fracture-filled. D. has undergone the HPHT process.

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PHOTO COURTESIES The Gemological Institute of America gratefully acknowledges the following people and organizations for their assistance in gathering or producing some of the images used in this assignment:

Argyle Diamonds, 23 (right) Ashton Mining Limited, 16 (top right) Bellataire LLC, 31 (top left) Chatham Created Gems, 12 (left), 13 (bottom) Diamond Promotion Service, 8 (left, center and bottom), 9 Diamond Trading Company, 7, 10 (top), 22 General Electric Research & Development Center, 3, 10 (bottom) The Home Shopping Network, 41 (bottom) Novatek, 29 (left) Superings, 11 (right) Victoreen, Inc., 27 (left)

46 1. Introduction: Beyond the Essentials

2. Birth of the Modern Diamond Industry

3. The Modern Diamond Market

4. How Diamonds Form

5. Exploring for Diamonds

6. Diamond Mining

7. The Diamond Crystal

8. Diamonds and Light

9. The Evolution of Diamond Cutting

10. Finding and Identifying Clarity Characteristics

11. Grading Clarity

12. Diamonds and Color

13. Grading Color

14. Grading Proportions—Table, Crown, and Girdle 4 / 2

15. Grading Proportions—Pavilion and 0 0

Culet—and Evaluating Finish 8

16. Grading Fancy Cuts

17. Estimating Weight, Recutting, and Repolishing

18. Diamond Simulants

19. Synthetics and Treatments

20. Succeeding in the Marketplace