diamonds&diamondgrading synthetics and treatments...

19Synthetics and Treatments

Diamonds & Diamond Grading

Table of Contents

Subject Page

Synthetic Diamonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Early Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Success and Progress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Applications in Industry and Jewelry . . . . . . . . . . . . . . . . . . . . . . . . 9Chemical Vapor Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Detecting Synthetic Diamonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Detecting CVD Synthetic Diamonds . . . . . . . . . . . . . . . . . . . . 20

Color Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Heat and Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Recognizing Color Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Clarity Treatments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Laser Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Internal Laser Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Fracture Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Detecting Fracture Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Disclosing Fracture Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

Treated Diamonds and the Marketplace . . . . . . . . . . . . . . . . . . . . . 39

Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

©©2002 The Gemological Institute of AmericaAll rights reserved: Protected under the Berne Convention.No part of this work may be copied, reproduced, transferred, ortransmitted in any form or by any means whatsoever without theexpress 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 andnatural colors.

SYNTHETICS AND TREATMENTS

People have revered the diamond as a precious product of nature forthousands of years. By now, you’ve learned about its progress fromsimple carbon atoms to rough diamond to finished gem. You understandhow diamond’s rarity gives it exceptional value in the gem world. Is itany wonder that, through the ages, alchemists and researchers have madecountless attempts to duplicate and enhance diamond’s unique propertiesand structure?

Through careful research, scientists have discovered ways to makenatural diamond “better”—to hide its imperfections or to make it a moreattractive color.

Benvenuto Cellini, the sixteenth-century Italian goldsmith and gemhistorian, wrote about early gemstone color treatments. He described theheating of sapphire, topaz, amethyst, and other gem minerals in fire untilthey lost their color—and imitated diamond.

Those early searches for diamond look-alikes later developed intosearches for techniques to make diamonds. Researchers tried to find just

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©1998 Tino Hammid

Key ConceptsDiamond’s beauty, rarity, and valueinspire research into synthesis andtreatment.

©2002 GIA. All rights reserved.

the right combination of ingredients, temperature, and pressure thatwould allow technology to do nature’s work. In the 1950s, scientistsbegan making synthetic diamonds. Now they’re widely used in industry,mostly in cutting instruments and abrasives. A few have been producedfor the gem market.

In this assignment, you’ll learn about synthetic diamonds and aboutcolor and clarity treatments, along with some basic detection skills. Nowthat 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 tohelp you meet that demand.

SYNTHETIC DIAMONDSn When was synthetic diamond first successfully grown?n How do synthetic diamonds fit into industry and the

jewelry market?n What are some basic detection methods for

synthetic diamonds?

As you learned in Assignment 18, there’s an important difference betweensynthetic diamonds and simulants. Synthetic diamonds are made in thelaboratory, and they have essentially the same chemical composition andcrystal structure as natural diamonds—or at least as close as researcherscan make them. Their physical and optical properties are nearly the sameas 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 theirchemical compositions and physical and optical properties are differentfrom those of diamond.

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19DIAMONDS AND DIAMOND GRADING

Michael Nicholson/Corbis

Sixteenth-century Florentine sculptorand goldsmith Benvenuto Cellini wrotesome of the earliest descriptions ofgemstone treatments.

Joseph Schubach

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

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

EARLY RESEARCH

In 1797, English chemist Smithson Tennant demonstrated that diamondwas nothing more than a very dense form of pure carbon. The fact thatcarbon was plentiful inspired researchers to explore the possibility ofturning some of it into much rarer diamond.

Through the 1800s and early 1900s, many researchers and chemiststried 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 diamondformation, but didn’t have the technology to produce the right conditions.

SUCCESS AND PROGRESS

Then, in 1941, Dr. Percy W. Bridgman, an American researcher whospecialized in high-pressure physics, came to an agreement with the GeneralElectric Corporation (GE) and other commercial parties. GE assigned

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

Bridgman to design a laboratory especially for the production of syntheticdiamonds. Before World War II interrupted the project, Bridgman and hiscolleagues made important advances in high-pressure technology—but nodiamonds.

In 1951, GE formed another research group to expand on Bridgman’swork. By 1953, they had designed equipment capable of reaching andmaintaining extreme pressures and temperatures. After that, the onlymodifications they made were to the apparatus that actually held andcompressed the raw materials.

Finally, a belt-type apparatus designed by team member Dr. Tracy Hallsucceeded. GE scientists created their first batch of synthetic industrialdiamonds in December 1954. After careful testing of the products andsuccessful repetition of the process, they announced the achievement tothe world on February 15, 1955.

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Hulton-Deutsch Collection/Corbis

Percy Williams Bridgman was one of the pioneers of diamond synthesis research.

A Swedish electric company—Allmana Svenska ElektriskaAktiebolaget—had actually made diamonds two years earlier. Theirscientists started some diamond-making projects in the 1940s, thenabandoned them. They began again in the early 1950s. In February 1953,they made several tiny synthetic diamonds. Even better, they were ableto 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 announcetheir accomplishment until two years after GE’s success. By then, it wastoo late for them to be recognized as the first diamond makers.

Today, almost all synthetic diamonds are grown using the processdeveloped 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 kepttheir process secret for the next two years under federally enforcedsecrecy regulations. GE filed worldwide patents in 1959, and the teampublished details of its procedures. De Beers soon followed with theirown patent for diamond synthesis.

You might think that the step from growing experimental batches oftiny synthetic diamond crystals to creating large, high-quality crystalswould be a relatively small one. But progress was limited. Larger crystalstake a lot longer to form than tiny ones. The challenge for researchers

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Bettmann/Corbis

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

Key ConceptsResearch into diamond synthesisbegan before 1800, but producersdidn’t succeed until the 1950s.

High pressure, high temperature(HPHT)—Diamond synthesismethod that mimics the pressureand temperature conditions thatlead to natural diamondformation.

was to increase crystal size and, at the same time, control the quality of thecrystals. 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 syntheticdiamonds. In 1970 and 1971, Lazare Kaplan and Sons of New York cutsome of those first gem-quality synthetic diamonds, which weighed about1 ct. each in rough form. Fashioned stones cut from those crystals rangedfrom 0.26 ct. to 0.46 ct. in weight, and from F to J in color. There werealso some yellows and blues, and the highest clarity was VS.

Over the next 14 years, a few synthetic gem-quality diamonds wereused for research and for special scientific uses. During this period, re-searchers solved the technical problems preventing large-scale manufacture.

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Both by Peter Johnston/GIA

All diamond presses work on the same principle: extremely high pressures andtemperatures applied to the necessary ingredients. This illustration shows the sixanvils in a modern diamond press. They’re pushed inward by pistons—that aren’tshown here—and exert enormous pressures on a tiny central container wherecrystal growth takes place.

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

anvil

high-pressure cell

carbonsource

metal flux

heatingelement

seed crystal

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 containisolated nitrogen atoms as trace elements. They add the chemical elementboron to provide electrically conductive blue Type IIb diamonds forcertain applications. They’ve also been able to produce some Type IIacolorless diamonds. Sumitomo markets its synthetics only for industrialand high-technology applications.

The synthetic industrial diamond market is dominated by two of itsoriginators: De Beers and GE. Production consists mostly of syntheticindustrial diamond grit. Its superior cutting and polishing abilities make itideal for use in a variety of tools, including drills, saws, and polishers.

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Robert Weldon/GIA

Most synthetic diamonds are small and yellow in color. These specimens—producedin Russia—range from 0.14 ct. to 0.88 ct.

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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).

Lowell Georgia/Corbis

APPLICATIONS IN INDUSTRY AND JEWELRY

Diamond’s properties of hardness, high thermal conductivity, opticaltransparency, and high electrical resistance make it uniquely suited formany high-technology applications. Industrial tools embedded withnatural or synthetic diamonds are used for machining alloy engine blocksand other automotive components. Some are designed for cutting naturalhardwoods, granite, and marble.

Scientific advances have made synthetic diamonds better than naturaldiamonds for many industrial uses. One advantage of synthetics is thatmanufacturers can control the growth process. Unlike natural diamonds,which nature fashions randomly, synthetics can be turned out in predictableshapes and sizes. Manufacturers can also control impurities and otheraspects of quality. In many cases, synthetic diamond grit outlasts naturaldiamond grit because of its uniformity.

Type IIa diamond—natural or synthetic—conducts heat more than fivetimes more efficiently than copper. This high thermal conductivity allowsit to take away the heat caused by the friction between moving parts. Thismakes it possible for a tool to operate under severe conditions withoutoverheating. “Slices” of large single-crystal synthetic diamonds are used

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Key ConceptsSynthetic diamonds are better formany industrial applications than natural diamonds.

for industrial and surgical tools, laser windows, and heat sinks, amongother things. (A heat sink draws unwanted heat away from an electronicdevice.)

Because of the extraordinary equipment and energy requirements, mostproduction of large synthetic diamond crystals in the 1990s was for exper-imental and research purposes only. Their presence in the jewelry marketwas limited by the high expense of producing colorless, cuttable diamonds.Bulk production of larger diamonds was limited because larger crystalstake longer to grow.

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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 offeredthem for commercial sale.

Key ConceptsThe use of synthetic diamonds injewelry is limited by high productioncosts.

In 1990, De Beers announced that the largest synthetic diamond grownto date was a 14.20-ct., industrial-quality yellow crystal, which took 500hours 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 Beersindicated that it was possible to grow crystals larger than 30 cts. in lesstime, but only some areas of the manmade crystals were gem quality.

In spite of these obstacles, a few companies around the world spentthe late 1990s preparing for full production of colorless, gem-quality,marketable cut diamonds. The challenge is that most HPHT syntheticdiamonds are either yellow or brown because it’s difficult to keepnitrogen out of the growing crystals. Manufacturers can produce bluediamonds 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 asolid material that, when melted, dissolves other materials. Special com-pounds added to the flux prevented nitrogen from entering the growingcrystal’s structure. De Beers also grew some colorless synthetic diamondsexperimentally for industrial applications.

GE and De Beers haven’t yet released their experimental diamonds intothe gem market. Russian scientists grew near-colorless synthetic diamondsfor the gem market, but never reached commercial production levels.However, during the 1990s, small quantities of colored syntheticdiamonds reached the gem market, distributed by a Thai-Russian jointventure in Bangkok, Thailand.

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Shane McClure/GIA

Most synthetic diamonds are yellowbecause it’s difficult to keep nitrogenout during the growth process. Thesethree platinum rings contain yellowRussian synthetic diamonds. They rangefrom 0.30 ct. to 0.40 ct., and are someof the few synthetic diamonds thatappear in jewelry.

Key ConceptsMost HPHT synthetic diamonds areyellow or brown because they containnitrogen impurities.

Tino Hammid/GIA

Russian scientists have successfullygrown near-colorless synthetic diamonds,but the stones have not appeared inthe commercial gem market in largequantities.

In the early 2000s, a US company called Gemesis Corporation beganmanufacturing and selling yellow and orange-yellow HPHT syntheticdiamonds 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 isChatham Created Gems. The company introduced a line of colored syn-thetic diamonds in yellows, blues, pinks, and greens. Their colors are lesssaturated than most colored synthetic diamonds, making them morenatural-looking.

CHEMICAL VAPOR DEPOSITION

In 2003, Apollo Diamond Inc., a US manufacturer, announced successfulgrowth of jewelry-size synthetic diamonds by a technique that doesn’trequire high pressure and uses relatively modest temperatures of 1346°Fto 2066°F (730°C to 1130°C). The method—called chemical vapor depo-sition (CVD)—was already in use for many industrial applications,including the production of high-purity thin films for semiconductors.Apollo adapted CVD to allow the deposition of synthetic diamond from acarbon-rich gas onto a silicon or diamond surface. The synthetic diamondgrows in thin layers, and its final thickness depends on the amount of timeallowed for growth.

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James Shigley/GIA

In the early 2000s, the GemesisCorporation began synthesizing yellow toorange diamonds for jewelry use (top).Many contain small metallic flux inclu-sions that can help with identification(bottom).

Maha Tannous/GIA

These synthetic diamonds, with their natural-looking colors, are from ChathamCreated Gems.

Chemical vapor deposition(CVD)—An industrial processadapted to allow growth ofsynthetic diamond from carbon-rich gas in thin layers onto asilicon or diamond surface.

Maha Tannous/GIA

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

DETECTING SYNTHETIC DIAMONDS

While researchers develop new and better production methods, the mainchallenges for the jewelry professional are detection and disclosure. Atrained gemologist can readily identify most HPHT synthetic diamondsusing 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 inclusionsthat natural ones do. A synthetic diamond won’t contain included mineralslike garnet, diopside, or even another diamond. The only inclusions asynthetic diamond might contain are dark, opaque remnants of the metallicflux it grew in.

These inclusions need to be examined closely. You can use fiber-optic lightto determine if they’re highly reflective or metallic looking. An inclusion ofmetallic flux can be conclusive evidence that the diamond is synthetic.

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Robert Weldon/GIA

Advances in CVD synthetic diamondgrowth have led to production of someattractive gem-quality stones.

Peter Johnston/GIA

In the CVD growth process, a microwave beam causes carbon to precipitate out of aplasma cloud and deposit onto a surface of diamond or silicon. As the carbondeposits build, synthetic diamond forms.

Both by John Koivula/GIA

As they grow, synthetic diamondsoften trap metallic bits of the flux thatsurrounds them. The bits becomeinclusions that are usually opaque andhighly reflective (top). They occur in arange of angular shapes, although thesquare shape (bottom) is fairly unusual.

A synthetic diamond won’t always have inclusions. One of the bestways to distinguish natural from synthetic diamonds is related to how theygrow, and to the shape of their crystals. Although a cutter can removethe exterior of a crystal during polishing, crystal growth structures likegraining and color zoning remain in the fashioned stone. These featurescan 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 temperaturesfor natural diamond crystal growth are higher than those used to grow

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With training and careful observation,gemologists can identify most syntheticdiamonds using standard gemologicaltechniques. In this case, inclusions ofhighly reflective metallic flux indicatethis diamond’s manmade origin. (19X)

The included mineral crystals in naturaldiamonds are more transparent andless obvious than the flux in syntheticdiamonds.

Natural diamond inclusions like thesecan resemble the flux in syntheticdiamonds.

The transparent, octahedral diamondcrystals in this fashioned diamond lookvery different from the metallic dark orshiny flux particles that decorate the inte-riors of many synthetic diamonds.

HPHT synthetic diamonds in the laboratory. At high temperatures,diamonds grow as octahedral crystals, but in the lower temperatures of thelaboratory, they grow as crystals with both octahedral and cubic faces.

Natural diamond crystals grow relatively equally in all directions froma small central core. Synthetic diamond crystals grow upwards andoutwards from a tiny seed crystal that’s placed on a flat surface. This leadsto an entirely different crystal shape, which looks like a broad-based,tapered pyramid terminated by a small flat face. This is a shape you’llnever see in a natural diamond.

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A vertical cross section of a syntheticdiamond shows its upward and outwardgrowth from the tiny seed crystal. Itscharacteristic zoned pattern forms whennitrogen atoms, which are present asimpurities during crystal growth, areconcentrated parallel to certain crystalfaces.

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 directionsfrom a central core, so a cross section through a crystal (left) reveals a concentricpattern 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.

NATURAL DIAMOND SYNTHETIC DIAMOND

cross section cross section

Blue fluorescence, concentricgrowth pattern

Yellow or greenish yellowfluorescence, cross-shaped

growth pattern

seed crystal

Because the shapes of natural and synthetic diamond crystals aredifferent, their internal growth patterns also differ dramatically. Thesegrowth patterns can be among the most reliable ways to separate naturalfrom synthetic diamond.

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Tino Hammid/GIA

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

John Koivula/GIA

This 0.78-ct. synthetic diamond has a flattened base where it grew upward from aseed crystal, which is visible at the center. This feature is typical of synthetics, butit’s never seen in natural diamonds, which grow by building layers from the insideout in all directions.

For example, the growth patterns related to the cubic and octahedralcrystal faces of the synthetic diamond can make an hourglass-shapedgraining pattern. Hourglass graining is often visible with magnificationthrough a fashioned synthetic diamond’s pavilion. Color zoning in syntheticdiamonds also follows the stone’s growth patterns. Natural diamonds won’tshow hourglass-shaped growth zoning.

If you can’t find any inclusions, graining, or color zoning, test thediamond’s reaction to UV radiation. This is particularly useful if you needto test an entire parcel of diamonds at the same time.

Natural diamonds that fluoresce typically display blue fluorescenceunder longwave UV, and a weaker, often yellow fluorescence under short-wave UV. Synthetic diamonds usually fluoresce yellow to greenish yellowunder both longwave and shortwave UV, and the reaction is usuallybrighter under shortwave UV. The synthetic diamond’s different crystalgrowth structures show up as a distinctive cross-shaped pattern to bothlongwave and shortwave UV.

In addition, many synthetic diamonds are phosphorescent: Theirfluorescent glow remains for a short time after the UV radiation is turnedoff. This feature makes it possible to examine several diamonds side byside. It’s unusual for a natural diamond to show phosphorescence.

Some synthetic diamonds are attracted to magnets because of the tinymetallic inclusions left behind from the flux metal used for diamond

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John Koivula/GIA

Even after a synthetic diamond is fashioned, it retains crystal growth structures thatproclaim its origin to the trained gemologist. An example is the surface graining onthe table facet of this Sumitomo synthetic.

Key ConceptsHPHT synthetic diamonds can beidentified by their metallic fluxinclusions, growth structures, andfluorescence.

Shane McClure/GIA

Because synthetic diamonds grow inan iron-based flux, they contain manymetallic inclusions. Some have so manymetallic inclusions that they respond toa magnet.

growth. Although some of the inclusions might be too small to be visibleeven under a microscope, you can test for their presence by suspending asynthetic diamond on a thread and holding a strong magnet near the stone.The metallic inclusions are attracted to the magnet, so when the magnetmoves, the synthetic diamond moves along with it. It’s extremely rare fora 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 technologyimproves, the quantity of metallic inclusions will decrease.

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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 hourglasspattern (above) is typical.

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. Bycontrast, under longwave UV, this Russian synthetic diamond (right) glows a greenishyellow color and has a distinctive cross-shaped fluorescence that reflects its differ-ent crystal growth pattern.

Nicholas DelRe/GIA

Gemesis developed its technology to the point where the visual charac-teristics that distinguish its synthetics are generally less obvious than thecharacteristics of other synthetic diamonds. The cutting process eliminatesmany of the remaining characteristics. Magnification might reveal colorzoning and small opaque or reflective metallic inclusions, but the inclusionsare often cloud-like and difficult to distinguish. Metal flux inclusions areoften parallel to a rough crystal’s outer surface, or found along boundariesbetween internal growth sectors.

Fluoresence varies more in Gemesis synthetic diamonds than it does inother synthetics. Gemesis synthetics can be inert under both LWUV andSWUV, or they might fluoresce a weak or very weak orange, possibly witha green cross-shaped pattern superimposed over it. The intensity of theSWUV reaction might be either slightly weaker or slightly stronger than theintensity of the LWUV reaction.

De Beers researchers developed two diamond-verification instrumentsin the mid-1990s for use in gemological laboratories: the DiamondSureand the DiamondView. The DiamondSure is a fairly simple instrument thatcan separate natural from synthetic colorless or near-colorless diamondsbased on the way each absorbs light.

It works because most natural near-colorless diamonds are Type Ia, sothey contain plentiful amounts of nitrogen. When nitrogen is plentiful indiamond, it causes a distinctive—and detectable—absorption pattern.So far, virtually all colorless synthetic diamonds that have been testedare Type IIa. Type IIa diamonds don’t show this distinctive nitrogenabsorption pattern.

The DiamondSure can test both mounted and unmounted gems. Thereare a few natural diamonds the DiamondSure can’t identify, but the instru-ment indicates if further testing is needed.

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James Shigley/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 aremore scattered than the clouds in natural diamonds.

Shane McClure/GIA

The diamonds that don’t pass the DiamondSure’s test can be positivelyidentified by the DiamondView. It’s a more complex, more expensiveinstrument that displays a diamond’s crystal growth structure as a patternof UV fluorescence, which is very different for synthetic diamonds thanit is for natural diamonds. It can help to separate natural from syntheticfor both near-colorless and colorless diamonds.

De Beers created these instruments for research purposes but plans toincrease production if gem-quality synthetic diamonds gain a greaterpresence in the industry.

DETECTING CVD SYNTHETIC DIAMONDS

CVD synthetic diamonds are faint brown to dark brown, near-colorless tocolorless, or light blue to intense blue. They might contain small, irregu-larly shaped, black inclusions that are probably graphite. The stones lackthe flux metal inclusions common in synthetic diamonds grown by high-pressure synthesis.

Some CVD synthetic diamonds fluoresce a very weak yellow-orangeunder LWUV, and a weak to moderate yellow-orange under SWUV. Othersare inert. Advanced testing reveals distinctive features in the absorptionspectra of these synthetic diamonds that separate them from other syntheticdiamonds and—more importantly—from natural diamonds.

The presence of synthetic diamonds in the marketplace will challengedealers and consumers to be more careful about diamonds in general. Ofcourse, disclosure should be the rule at every step of a syntheticdiamond’s journey through the market, as well as during an appraisal. Butyou might not always be told that a diamond is synthetic. Whenever youcome 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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Eric Welch/GIA

De Beers’ DiamondView relies on the different fluorescence patterns of natural andsynthetic diamonds to separate them. The instrument consists of a fluorescenceimaging unit, a TV camera, and a specially programmed computer. A trained operatorevaluates the stone’s image to determine its origin.

Key ConceptsCVD synthetic diamonds lack the fluxmetal inclusions that are common inHPHT synthetic diamonds.

COLOR TREATMENTSn What factors encouraged development of diamond color

treatments?n How does heat affect treated diamond color?n How did a modern color-modification process evolve from

diamond synthesis?n What are some clues for detecting color treatments?

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

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©1998 Tino Hammid

These diamonds are natural, but they owe their beautiful colors to laboratorytreatments.

Creative marketing of naturally coloreddiamonds in the 1980s and 1990shelped increase public awareness anddemand for these rare natural treasures.

As you learned in Assignment 12, diamond color comes from thepresence of impurities or the effect of distortions or defects in a diamond’scrystal lattice. Diamonds tend to be yellow when nitrogen is present as animpurity and blue when the impurity agent is boron. Green diamonds gettheir color when radiation displaces atoms from their normal positions inthe crystal lattice. And the color in pink and brown diamonds is due tograining, 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 inthe lab. Since then, scientists have experimented with many ways tochange or modify diamond color. The value and rarity of naturally coloreddiamonds have inspired many struggles to create their colors in the lab.

IRRADIATION

Natural radiation in the ground makes the diamonds near it turn green. Inthe early 1900s, Sir William Crookes tried to duplicate nature’s processand manufacture green diamonds in the laboratory. Crookes’ experimentsmarked early research into color-treating diamonds by artificial irradia-tion. He found that he could make diamonds turn green by burying them ina radium compound for up to a year. Unfortunately, the treatment alsomade the diamonds highly radioactive.

Atomic science researchers invented the cyclotron soon after WorldWar II for nuclear research. It was a large machine that acceleratedatomic particles around a circular path. Its introduction encouragedmajor developments in irradiation, and made artificial irradiation of

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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 laboratoryprocess is so similar to natural irradiation that it would be otherwise impossible toprove the origin of its color.

Irradiation—Exposure of a materialto radiation; causes color changein diamonds.

Linear accelerator—A machineused to accelerate electrons tohigh energy along a straight path.

diamonds in commercial quantities possible. But this treatment resultedin only shallow penetration of the atomic particles into the diamond, soit caused distinctive color zones.

Later in the 1900s, researchers developed the linear accelerator. Italso accelerates atomic particles, but along a straight path rather than acircular one.

Today, penetration with high-energy electrons in a linear accelerator isone of two frequently used irradiation techniques. Depending on thematerial and treatment conditions, this process usually produces blue orblue-green colors. The other technique involves bombardment withneutrons, usually in a nuclear reactor. Diamonds treated this way usuallybecome green, blue-green, or dark green.

Both of these modern processes produce uniform color without zoningbecause the electrons and neutrons penetrate very deeply. And theradioactive atoms in diamonds treated with either process usually haveshort half-lives, so the diamonds lose their radioactivity before they’rereleased into the market.

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Roger Ressmeyer/CorbisBettmann/Corbis

The first irradiated diamonds were treated in a cyclotron, a large device developedfor atomic research (above). Today, most diamond treaters use more compactequipment, like a linear accelerator (right).

Half-life—The length of timerequired for half of a group ofatoms of a particular type(radioactive) to decay intoanother type (non-radioactive).

Key ConceptsModern diamond irradiation methodsleave little or no color zoning and noradioactivity.

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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.

one half-life

four half-lives

six half-lives

ten half-lives

After one half-life, half of the radioactivityremains.

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

Scientists use half-life to measure the long period of radioactivity in amaterial. They define a half-life as the amount of time required for halfthe radioactive atoms of a substance to become non-radioactive. Once thefirst half decays in this way, the “clock” resets and half of what’s leftbegins to decay. Then half of that must decay. This process continues untilhalf of what’s left is an undetectable amount. A half-life can vary fromless than a second to billions of years.

The Geiger counter is a fairly simple and affordable instrument that candetect and measure moderate to high levels of radioactivity. At the otherend of the scale are complex instruments used by research labs.

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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 avaluable tool to have on hand, especially if you deal in estate jewelry, which is morelikely 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, greendiamonds can be very attractive.

Many countries have government agencies that regulate the amount ofradioactivity allowed in gemstones. In the US, the Nuclear RegulatoryCommission (NRC) regulates manmade radioactivity. At one time, theirregulations applied only to gems irradiated in a reactor. A law that passedin 2005 and took effect in 2007 extended their control to gems irradiatedin accelerators, which includes most irradiated diamonds.

The Commission allows radioactive gemstones to be released to thepublic only after they’re tested by an NRC-licensed organization. Thetesting 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.

Sometimes, the release date is far in the future. Some gems irradiatedin the early to mid-1900s are still radioactive.

Color-modifying irradiation treatment usually comes after a diamondis cut and polished. Unfortunately, irradiated colors are sensitive to heat.Technicians use cold running water to prevent color changes during theirradiation process, which generates a lot of heat. After the gem is set,the heat from jewelry repairs, recutting, or repolishing might also changeits color.

ANNEALING

A controlled heating and cooling process called annealing, which youread about in Assignment 12, is another way to change diamond color.When it follows irradiation in a two-step process, annealing modifiesirradiated colors to produce brown, orange, or yellow. Rarely, it can alsoproduce shades of pink, red, or purple. In the 1970s, many diamond colorswere modified this way.

Annealing is also sometimes used alone. The process changes diamondcolors in a series—generally blue to green to brown to yellow—and thetreatment is stopped when the desired color is reached. In the early 1990s,treaters discovered it was possible to treat typical yellow to brownsynthetic diamonds to produce more marketable reddish colors.

As with irradiation, if heat is later applied to an annealed diamondduring routine repairs, it can drastically alter its color.

HEAT AND PRESSURE

In the late 1990s, advances in diamond synthesis led scientists toexperiment with ways to modify diamond color using the same HPHTequipment. Those experiments resulted in two different processes. Oneprocess improves the color of brownish Type IIa diamonds, making themalmost colorless. The other creates green or yellowish green diamondsfrom brown Type Ia ones.

After HPHT processes were developed for commercial use, the GIALaboratory and other gemological labs explored ways to detect theirpresence.

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Key ConceptsHeat can alter irradiated colors.

Annealed diamond color can changeif it’s exposed to heat during routinerepairs.

Shane McClure/GIA

This 0.55-ct. synthetic diamond wasoriginally brownish. A combination ofirradiation and heating turned it anattractive red.

GE—the same company that pioneered diamond synthesis—selectedType IIa diamonds for HPHT processing. Type IIa diamonds are very rarein nature: They make up less than 1 percent of diamonds mined. Theyhave a very pure chemical composition, and only very small amounts ofnitrogen 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 notthrough other types, so gemologists can take advantage of this property toseparate them.

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Both by Phillip Hitz/Gübelin Gem Lab

HPHT processing can dramaticallyimprove a diamond’s color. Beforeprocessing, these Type IIa diamondsranged from N-color to Fancy Lightbrown (top). After processing by GE,their color improved significantly, andthey received color grades of D to H(bottom).

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

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THE DEEPDENEWeight: 104.88 cts., then 104.52 cts.Cut: CushionColor: Light yellow to deep green to golden yellow (treated color)

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

The Deepdene: Treated, and Treated Again

Christie’s Images Inc.

Christie’s auction house sold the Deepdene diamond in 1997, set in a beautifulcultured pearl and diamond choker necklace.

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In the early 1900s, Helena Bok,a Pennsylvania socialite, boughtthe diamond. She named itDeepdene, which means “deepvalley” in old English, to honorher family’s estate. The Bok familyloaned it to the PhiladelphiaAcademy of Sciences, which dis-played it publicly in the 1940s.The family sold the diamond toHarry Winston in 1954, andWinston sold it the followingyear.

Sometime after that, theDeepdene was irradiated in acyclotron, which turned it a hand-some green color. The treatersrecut the culet and pavilionslightly to eliminate the umbrella-shaped color zoning left by theradiation treatment. That’s whenits weight changed to 104.52 cts.

The diamond was sold again in 1971. By that time, theDeepdene was yellow again. When questions arose about the originof its color, gemological expert Dr. Eduard Gübelin stepped for-ward. He said that he had examined the diamond and determinedthat it was annealed. It’s said that Dr. Gübelin also sent the diamondto Robert Crowningshield at GIA, who agreed that its yellow colorwas the result of heat treatment.

In November 1997, the Geneva branch of Christie’s auctionhouse sold the Deepdene at auction. GIA Laboratory had examinedit a few months earlier and pronounced it VS1 clarity. This time, thegem was surrounded by four rows of cultured pearls and diamondsin 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 originalDeepdene. Experts solved the mystery by obtaining a photograph ofthe original gem from Helena Bok. They compared the photographto the actual diamond under a special microscope that magnifiedthem both 12.5 times and displayed the images side by side. Theproof was an identical natural, just above the girdle. It convincedresearchers that they held the original Deepdene diamond.

Christie’s Images Inc.

In 1997, Christie’s photographed theDeepdene diamond out of its setting.This side view shows its lovely treatedyellow color.

Most Type IIa diamonds have very few clarity characteristics beyondsmall fractures and tiny mineral inclusions. Many have clarity grades ofVVS or better, and HPHT processing doesn’t significantly affect mostinclusions or clarity grades. GE selects diamonds with the highest possibleclarity for processing.

As you learned in Assignment 12, some Type IIa diamonds are brown.The brown color is caused by internal, parallel grain lines, which are actu-ally distortions of the diamond’s crystal structure. These are the diamondsthat GE processes with HPHT. High pressures and temperatures eliminatethe brown color by reducing or removing these structural irregularities.

The first commercial release of HPHT diamonds occurred in March1999. The release was the result of a partnership between GE and majordiamond manufacturer Lazare Kaplan International (LKI). The companiesdeclared that the gems had been processed to improve color, brightness,and brilliance and that the results were permanent and also irreversible.

At first, the stones were known as GE-POL or “Pegasus” diamondsbecause they were marketed through Lazare Kaplan’s subsidiary, PegasusOverseas Limited (POL). At present, they’re sold by LKI under the brandname “Bellataire.”

GE and Lazare Kaplan cooperated with GIA and other leading gemlabs to help identify defining characteristics for the processed diamonds.They supplied samples of diamonds both before and after processing forthe labs to compare and analyze.

High temperatures and pressures are risky for some diamonds. Somemight break from thermal shock, while others might become chipped orfractured. 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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After HPHT processing, some cleavages take on a granular,reflective appearance.

In some HPHT diamonds, solid inclusions surrounded bystress cracks display a black inner area of graphite and abrighter halo of outwardly radiating cracks. (40X)

Key ConceptsHPHT eliminates the structuraldistortions that cause brownishcoloring in some Type IIa diamonds.

HPHT can dramatically improve the color and value of brownish diamonds.

Graphitization—Graphite forma-tion around a diamond’s mineralinclusions and feathers thatresults from the extreme condi-tions of HPHT processing.

Most diamonds need repolishing after HPHT processing, but theimprovement in color and value can be dramatic. Brown diamonds of Nto O color, and even Fancy Light brown diamonds, can attain D to Hgrades after HPHT processing.

Other manufacturers use similar processes to alter diamond color.They’ve been able to produce intense yellow to greenish yellow stonesfrom brownish Type Ia diamonds. Many diamonds that were modified thisway 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 HPHTemerged. This changed in recent years with the introduction of a newcoating method developed and marketed by Serenity Technologies.

These modern silica coatings are applied to polished colorless or near-colorless diamonds. The process results in a variety of natural-lookingfancy 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 disclosureare vital when handling coated color-treated diamonds.

RECOGNIZING COLOR MODIFICATIONS

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

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Darren Rosario

The Bellataire inscription on this diamond identifies it as onethat has undergone HPHT processing.

John Koivula/GIA

High pressures and temperatures can result in the formationof graphite around a diamond’s mineral inclusions. (40X)

Jessica Arditi and Jian Xin (Jae) Liao

A new coating technique can produce avariety of colors on polished diamonds.These stones range from 0.01 to 0.70 ct.

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Shane Elen/GIA

After HPHT processing, this diamond’s surface displayed etching and pitting. Thisstone will require repolishing before it can be sold. (10X)

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.

Both by Maha Tannous/GIA

Some of these brown diamond crystals (above) turned a more desirable greenish yel-low (left) after HPHT processing.

expensive instrument that reads a gem’s light absorption across thevisible, UV, and infrared ranges. Experienced technicians can interpretthat information and usually turn it into an origin-of-color judgment.

There are some clues to color treatments that you can detect undermagnification, with fairly simple equipment. As you’ve learned, colorzoning parallel to facet junctions is one sign of a cyclotron-irradiateddiamond. If a brilliant cut is irradiated from the pavilion, the color zone isan 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 youplace the stone on a white surface and look at it through the pavilion. Ifyou see either type of color zoning, you should send the diamond to agemological laboratory for further testing.

Whether green diamonds came by their color naturally or artificially isalmost impossible to determine, even with sophisticated laboratory tests.That’s because all green diamonds are irradiated. Some are irradiatednaturally in the earth, and some by scientists in the lab.

Identifying HPHT-processed diamonds involves specialized laboratorytechniques like spectroscopy and photoluminescence. But it might bepossible to detect some signs of HPHT processing with microscopeexamination. Those signs include damage caused by the extreme heat andpressure conditions, like etched or frosted naturals and fractures thatappear frosted or that converted to graphite. You’ll see graphitization in theform of darkened areas in fractures and around feathers.

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

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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 pinkand yellow zones in this 0.43-ct. diamond (right).

Since this is a rough crystal, it’s easy toassume that its green color is natural,but rough can also be irradiated in thelaboratory.

Key ConceptsMost origin-of-color tests should bedone by a gemological laboratory.

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

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

LASER DRILLING

Since the early 1970s, diamond manufacturers have used lasers to drilltiny tunnels—thinner than a human hair—into diamonds to reach darkinclusions. The process uses a carbon dioxide laser to heat a tiny area ofthe diamond until it evaporates, producing a tiny tube that the operator candirect toward an unsightly inclusion.

The laser drill-hole makes it possible to vaporize the inclusion with thelaser, bleach it, or etch it out with acid. This lightens a dark inclusion,which can make the diamond more marketable.

In spite of the fact that it disguises an existing inclusion, laser drillingoften doesn’t improve the clarity grade. In fact, the drill-hole itselfbecomes a clarity characteristic. The drill-hole shouldn’t cause a durabilityproblem, but if it fills with foreign material, it becomes more visible.

You might be able to detect a laser drill-hole with careful examinationunder 10X magnification, but higher magnification is often necessary. Youcan distinguish laser drill-holes from etch channels—natural, hollow, tube-like features present in some diamonds—by the fact that laser drill-holesare circular in cross section, while etch channels are square, triangular, orhexagonal.

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Before laser drilling, dark includedcrystals stand out in high relief againstthe rest of the diamond (top). After thediamond is laser drilled and the crystalsare bleached with acid, they’re muchless obvious (bottom).

Vincent Cracco/GIA

In this close-up of a laser-drilled diamond,you can clearly see the drill-hole betweenthe surface and the inclusion, which wasbleached to be less visible. (63X)

Some diamonds contain natural featurescalled etch channels, which are angularand can display growth marks. By con-trast, laser drill-holes are cylindrical andlack any features resembling growthmarks.

Laser drilling—Using a concen-trated beam of laser light to reacha diamond’s dark inclusions anddisguise or eliminate them.

Key ConceptsLaser drilling can make a diamondmore marketable by improving itsappearance.

Because laser drill-holes arepermanent, gem labs report themas clarity characteristics.

Fracture filling makes a diamond’sfractures less reflective by using ahigh-RI glass filler.

Fracture filling is the most commondiamond treatment.

It’s difficult to see a laser drill-hole if it’s very short or covered by aprong in a setting. Once drilled, the hole is a permanent characteristic ofthe diamond, so all major gem labs grade laser-drilled stones and reportthe drill-hole as a clarity characteristic.

At one time, some industry professionals considered laser drilling apart of the cutting process, and didn’t think it required any specialdisclosure or description. But now, there’s industry-wide agreement thatlaser-drilled diamonds should be clearly disclosed all the way fromwholesaler to consumer.

INTERNAL LASER DRILLING

A variation on laser drilling is called internal laser drilling (ILD). It’s atechnique that uses a laser to expand an existing cleavage or create a newcleavage between an inclusion and the surface. This allows the introductionof a bleaching solution. The result is the lightening of a dark inclusion,making it less visible.

The cleavage created by this procedure is more natural-looking than atraditional laser drill-hole. When you examine a diamond treated withILD 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 the1980s. 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 substanceis infused into a diamond’s fractures.

As you learned in Assignment 8, the refractive index (RI) of diamondmakes light behave in a predictable way. When a diamond has a fracturethat reaches the surface, the air in the fracture (with its lower RI) inter-rupts light’s path through the diamond and makes the fracture reflectiveand easier to see. The filling’s RI is closer to diamond’s than to the RI ofthe air it replaces, so it makes the filled fracture almost invisible to thecasual 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-able for gem use can now be treated and made attractive and affordable toa wider range of consumers.

Those who never thought they could afford a diamond over a caratsuddenly find they can own a larger fracture-filled diamond. This is alsoan advantage to the affluent customer who is looking for a “fun” diamond—one that’s flashy but not necessarily expensive. Fracture filling might alsobenefit a customer who accidentally cracks a diamond and is looking fora way to make that diamond look almost new again.

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Both by Vincent Cracco/GIA

The white feathers in this 1.39-ct. FancyIntense pink emerald-cut diamond (top)detracted from the stone’s color. Afterthe diamond was fracture filled (bottom),most of the feathers became transparent,and the stone revealed a more highlysaturated pink color.

Internal laser drilling (ILD)—Aclarity treatment that uses a laserto expand an existing cleavage orcreate a new one, allowing theintroduction of a bleachingsolution.

Vincent Cracco/GIA

Internal laser drilling resulted in theunnatural, irregular, wormhole-like chan-nels in this diamond. (63X)

Diamonds as small as melee have been filled, but because of the costof the treatment, most filled diamonds are over one carat. This is becausethe marketability of larger stones takes a higher leap with an improvementin apparent clarity.

Fracture filling has its advantages—it makes a diamond look better—but it also has some disadvantages. For one thing, the filler sometimeslowers a diamond’s color slightly.

Fracture filling can last for years with proper care, but it’s important toknow that the fillers can sometimes be damaged by common jewelryrepair procedures. Damaging conditions include the high temperaturescreated during recutting or repolishing and the torch heat generated duringretipping or repair. Over time, repeated cleaning can also harm fillers,especially when the method involves steam, acid, or ultrasonics. Prolongedexposure to UV radiation—even sunlight—can discolor a filler and makeit look cloudy over time.

Some damage is reversible, some is not. It’s possible to replace the fillerif 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 ontheir treatments for just this reason. But those assurances of quality are notenough for everyone. While some jewelry stores carry a selection of filleddiamonds, others refuse to accept them from their suppliers.

DETECTING FRACTURE FILLING

The ability to identify filled diamonds is always essential. It’s importantif you have to take jewelry in for repair because everyday repair andcleaning procedures can damage treated stones. And it’s obviously importantwhen you buy or sell diamond jewelry. Your firm’s reputation suffers ifyou sell a fracture-filled diamond without disclosing the treatment. This

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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 refractslight almost as well as the surrounding diamond, so the fractures are less apparent.

John Koivula/GIA

Jewelry repair procedures can damagediamond fillers. The heat from a jeweler’storch caused tiny beads of melted fillerto leak out of this diamond’s fracture.(50X)

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 offracture filling is called the flash effect, which is a flash of changing colorthat shows up with proper lighting under magnification. The flash effectresults because glass fillers don’t precisely match diamond’s RI for allwavelengths of light. To see it, you must look parallel to the fracture androck the diamond back and forth.

Other signs of fracture filling include gas bubbles trapped in the fractureor 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’renot part of the diamond’s original internal structure.

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Vincent Cracco/GIA

This diamond has multiple laser drill-holes and a pinkish purple flash effect thatshows it’s also fracture-filled. (37X)


This diamond’s fracture wasn’t completely filled, so it contains large bubbles oftrapped gas. This is one of the features to look for when you suspect the presenceof fracture filling. (35X)

In some fracture-filled diamonds, the fillerhas a crackled texture. It’s very obviouswhen the filled fracture is fairly thick.

Key ConceptsSome signs of fracture filling are theflash effect, trapped bubbles, and acrackled texture.

A few things can make detection a little more difficult. One small filledfracture is more difficult to see than several, and requires more carefulexamination. 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 thediamond from many different angles. Fiber-optic illumination makes theflash effect more evident.

Because fracture fillings can be semi-permanent, most gemologicallaboratories, including the GIA Laboratory, don’t grade filled diamonds.They do, however, report the presence of fracture filling. Its only functionis 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 coulddepend on proper identification and disclosure of this or any other treatment.

DISCLOSING FRACTURE FILLING

Since its introduction, the industry has debated methods of disclosingfracture filling without alarming the customer. An early solution was theterm “clarity enhancement,” which had a more positive sound than “fracturefilling.” But the US Federal Trade Commission and others in the industryconsider the words “clarity enhancement” misleading. It was soon followedby the term “clarity treatment,” which was adopted by many industryprofessionals as the preferred—and more correct—term.

International diamond professionals and regulatory agencies demanddisclosure of fracture filling every time a diamond changes hands. Youmust tell your clients that they’re buying a fracture-filled diamond andinform them of its special care requirements. They must also understand

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Nicholas DelRe/GIA

It’s always important to be aware of the presence of fracture filling because ordinaryjewelry repair procedures can damage the filler. This 3.02-ct. diamond was mountedin a ring. During the repair process, the heat from the jeweler’s torch darkened thefilling and dramatically affected the diamond’s appearance.

Key ConceptsDisclosure of fracture filling is anindustry requirement.

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 therepair 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 jewelerswho were selling undisclosed fracture-filled diamonds. The shockingnews set the trade buzzing, not only in the city where the deceptionoccurred, but all over the US. Since then, consumers have become betterinformed about diamond treatments.

Many manufacturers of diamond fillers have prepared informativevideos and printed materials to help with treatment disclosure. The videosserve a dual purpose. Besides educating customers, they also teach retailersand suppliers about this technology.

TREATED DIAMONDS AND THE MARKETPLACE

In the last 10 years, diamond treatments have become much more of anissue in the jewelry trade. As modern clarity and color treatmenttechniques make many diamonds more marketable, the need for positive,ethical disclosure grows. Most gem professionals, in an effort to preservetheir customers’ trust, have been much more careful about detecting anddisclosing treatments of all kinds.

There are far more treated diamonds in the marketplace than there aresynthetic diamonds. Although synthetic diamonds are grown widely forindustrial uses, it’s still too costly and time consuming to produce syntheticdiamonds on a wide scale for use in jewelry. Even so, it’s important to stayaware of the possibility that a few synthetics might exist in the marketplace.

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

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

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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.

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Diamond’s beauty, rarity, and value inspire research into synthesis and treatment.

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

Synthetic diamonds are better for many industrial applicationsthan natural diamonds.

The use of synthetic diamonds in jewelry is limited by highproduction costs.

Most HPHT synthetic diamonds are yellow or brown becausethey contain nitrogen impurities.

HPHT synthetic diamonds can be identified by their metallicflux inclusions, growth structures, and fluorescence.

CVD synthetic diamonds lack the flux metal inclusions thatare common in HPHT synthetic diamonds.

Modern diamond irradiation methods leave little or no colorzoning and no radioactivity.

Heat can alter irradiated colors.

Annealed diamond color can change if it’s exposed to heatduring routine repairs.

HPHT eliminates the structural distortions that cause brownishcoloring in some Type IIa diamonds.

HPHT can dramatically improve the color and value of brownish diamonds.

Most origin-of-color tests should be done by a gemologicallaboratory.

Laser drilling can make a diamond more marketable byimproving its appearance.

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

Fracture filling makes a diamond’s fractures less reflective byusing a high-RI glass filler.

Fracture filling is the most common diamond treatment.

Some signs of fracture filling are the flash effect, trappedbubbles, and a crackled texture.

Disclosure of fracture filling is an industry requirement.

Key Concepts

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Chemical vapor deposition (CVD)—An industrialprocess adapted to allow growth of syntheticdiamond from carbon-rich gas in thin layers onto asilicon or diamond surface.

Graphitization—Graphite formation around adiamond’s mineral inclusions and feathers thatresults from the extreme conditions of HPHTprocessing.

Half-life—The length of time required for half of agroup of atoms of a particular type (radioactive) todecay into another type (non-radioactive).

High pressure, high temperature (HPHT)—Diamond synthesis method that mimics thepressure and temperature conditions that lead tonatural diamond formation.

Internal laser drilling (ILD)—A clarity treatment thatuses a laser to expand an existing cleavage orcreate a new one, allowing the introduction of ableaching solution.

Irradiation—Exposure of a material to radiation; causes color change in diamonds.

Laser drilling—Using a concentrated beam of laserlight to reach a diamond’s dark inclusions anddisguise or eliminate them.

Linear accelerator—A machine used to accelerateelectrons to high energy along a straight path.

Synthetic diamond—Manufactured diamond withessentially the same physical, chemical, and opticalproperties as natural diamond.

Key Terms

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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. Whenyou’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. XenocrystB. Metallic fluxC. Garnet crystalD. Diopside crystal

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.

CONTINUED NEXT PAGE...

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________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-raysB. Radium compoundC. Ultraviolet radiationD. 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.

CONTINUED NEXT PAGE...

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________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 effectB. Hourglass grainingC. Etched or frosted naturalsD. 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 COURTESIESThe Gemological Institute of America gratefully acknowledges the following people and organizationsfor 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)

11. Grading Clarity

12. Diamonds and Color

13. Grading Color

14. Grading Proportions—Table, Crown,and Girdle

15. Grading Proportions—Pavilion andCulet—and Evaluating Finish

16. Grading Fancy Cuts

17. Estimating Weight, Recutting, and Repolishing

18. Diamond Simulants

19. Synthetics and Treatments

20. Succeeding in the Marketplace

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 ClarityCharacteristics

4/2008

diamonds&diamondgrading synthetics and treatments...

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