By now, you’ve probably seen press releases from AGA (Accredited Gemologists Association) and GCAL by Sarine, announcing the new Hybrid Master Set—a diamond color comparison tray that includes both synthetic and natural diamonds—soon to be available from Stuller.
As you may know, grading the color of near-colorless and colorless diamonds requires a comparison set of GIA color-graded diamonds, known as a Master Set. Each Master Stone represents the highest position within its grade. For example, an E Master Stone is the highest E color possible—closest to D, and farthest from F.
So when comparing a diamond to the E Master:
▻If your diamond shows less color, it’s graded D.
▻If it shows more color than the E Master, you move on and compare it to the F Master, and so on.
So where do you get a Master Set?
Great question!
For the past 20 years, it has been virtually impossible to acquire a Master Set!
And this is where our story begins… with the Canadian Jewellers Association (CJA) on a virtual online roundtable discussion with representatives from the AGA, GIA (Gemological Institute of America), the CGA (Canadian Gemmological Association), ASA (American Society of Appraisers), and AGS (American Gem Society) all asking the same question, “Where do we get a Master Set?”
After two years of hard – and very frustrating – work, with major cooperation, and some very smart work-arounds, here is the story of how the Hybrid Master Set, against all odds, became a reality!
Gary Roskin
Roskin Gem News Report
If you buy and sell diamonds, then you are familiar with a diamond’s core value factors: the 4 Cs – Color, Clarity, Cut, and Carat Weight.
For this story, we are going to focus on Color, specifically, color grading. To grade color, you need to have a set of GIA color-graded diamonds for comparison – a Master Set.
A Brief History
The Basics of GIA’s Color Grading Scale
The Gemological Institute of America (GIA) is the school that created the internationally accepted diamond grading system, which includes the color grading scale: colorless to light yellow, beginning at the letter D, being completely colorless, and moves through the alphabet, D, E, F being colorless, G, H, I, and J, being near colorless, K, L, and M being faint yellow, etc. each letter gaining a little more yellow body color as the scale progresses through Z.
To determine a diamond’s color grade, you rely either on a professional diamond grading laboratory to tell you what the color is, or you use a Master Set to compare against the color of the diamond you are buying, selling, or appraising.
Because each color grade is a range, from high to low, only diamonds with a color of the very highest in a particular grade can even begin to qualify as a Master Stone. From there, the basic requirements needed are (in no particular order):
▻having no imperfections that get in the way of seeing the diamond’s body color,
▻having good proportions including a decent crown height and girdle thickness,
▻having an evenness of color,
▻little or no fluorescence,
▻of similar size, etc.
Availability
Unless you already have a Master Set, the big problem for diamond merchants, jewelers, and appraisers is acquiring one. GIA-graded Master Sets are rare – some might even say nearly impossible to find.
Back in the 1960s, ’70s, and ’80s, GIA’s Gem Trade Lab would have had boxes of diamonds on hand from American diamond cutters C.A. Kiger, J.C. Keppie, and Lazare Kaplan, all cut to “ideal proportions,” in quarter-carat and one third-carat sizes, to create Master Sets for retail jewelers. Today, not so much.
Build a Set Today
These days, unless you’re a diamond manufacturer with access to inventory, creating a diamond color grading Master Set just isn’t practical.
▻They are expensive (thousands of dollars in diamonds alone)
▻It can take many months to acquire the right set of diamonds.
… and
▻Finding a diamond manufacturer who has the inventory necessary and is willing to take the time, work with GIA to help you build a set, is highly unlikely.
An Old Set
Occasionally, a GIA-graded Master Set may come up for sale—when a jeweler goes out of business, for example. But there’s no guarantee the diamonds are the originals from the set; one or more may have been accidentally swapped out or sold over time. And even if they are original to the set, they may no longer meet today’s grading standards to qualify as Master Stones. (example – a 4-stone set that sold for $2800 in 2007)
So what to do?
Everyone in the diamond business should have a Master Set. Even if you use an electronic grading device, or only work with lab-graded diamonds, it’s still important to compare a diamond against a Master Set—so you can see the color for yourself.
Here’s One Solution When you can’t find – or afford – a Diamond Master Set
Master Sets made up of Cubic Zirconia, (example) a well-known diamond imitation, are available in the market. For the most part (yes, there are exceptions) they come with several challenges:
▻They are not graded by GIA.
▻Some reportedly change color over time
▻Some tend to be slightly brownish in color
▻Their brilliance and transparency are different than diamond
Simply put, they are not diamond. That said, with a bit of practice (getting used to the obvious differences between CZ and diamond), they can be useful. And most importantly, they are available and very affordable.
Enter the Accredited Gemologists Association (AGA)
As an association, the AGA has several levels of membership, along with special member recognitions, one being the AGA Certified Gemological Laboratory (CGL) designation. One of the requirements to become a designated AGA Certified Gemological Laboratory – specifically one that evaluates diamonds – is that you have a diamond color-grading Master Set. But with the impossibility of acquiring a Master Set, members looking to certify their lab are simply out of luck. And AGA has not been happy about that for years.
And THIS is where our story begins!
Alberto Scarani
Heading up the challenge for the AGA Board of Directors is Alberto Scarani, Bonanno Award recipient from 2019, recognized for his work in computerized spectroscopy, and co-owner of MagiLabs, designing and manufacturing hi-tech spectroscopy units for gem identification.
Scarani recalls how the quest for finding Master Sets got started.
TWO YEARS in the Making
“In the beginning, almost two years ago, the membership coordinator of the Canadian Jewellers Association (CJA) organized a virtual online roundtable to discuss the issue about the impossibility of acquiring a Master Set. Besides representatives from the AGA, invited to the meetings were those from GIA, the CGA – the Canadian Gemmological Association, ASA – the American Society of Appraisers, and AGS – the American Gem Society”
“Even if there were initially a collective effort to collaborate in finding a solution, after a couple of meetings, even with selected people from the group, it seemed it was impossible to find a source for all the diamonds needed for making Master Sets.” Scarani and others were finding no solutions. “At some point, the idea of using synthetic diamonds came up.”
Synthetic Diamonds Could Dramatically Reduce the Cost
With cost always a key consideration, the ideal solution would be a Master Set made up entirely of synthetic diamonds. This could potentially keep the total cost under $5,000, with most of the expense going towards the physical production of the set, rather than the diamonds themselves.
But There’s a Huge Problem with Synthetics
“The main challenge in using synthetics was questioned straight away, due to the issue of their mainly brown and grey overtones,” says Scarani.
Certainly, GIA would reject any diamond that had a brownish or greyish tint. They are just not suitable for a Master Stone.
How are we doing?
▻The group can’t find a willing diamond manufacturer.
▻They have concerns about synthetics showing a brownish tint.
▻GIA will not grade synthetic diamonds for Master Stones, so this is not an option.
So does Scarani give up now?
There Must be a Way
Scarani was determined to see this through. “I already knew that GIA was not available to create a synthetic Master Series.” That brownish tint is a deal breaker. But what if we eliminate the brownish synthetics, and now just focus on the yellow synthetic diamonds? Is that possible?
Seeing Yellow – The Question of Spectroscopy
As mentioned earlier, Alberto Scarani is an expert in spectroscopy. For context, GIA uses Type Ia diamonds in its Master Sets. These Type I diamonds, part of what’s commonly called the ‘Cape Series,’ show varying degrees of yellow body color due to N3 centers in their crystal structure. Spectroscopy can measure these variations and plays a role in the technology of color grading machines.
It’s important to recognize that synthetic Type II diamonds lack N3 centers and have entirely different spectral characteristics. As a result, you cannot use standard (spectral) color grading machines to grade synthetic diamonds. While synthetic diamonds can have yellow body color due to nitrogen, they do not show the same spectra as a natural diamond.
Would this be a problem? Turns out, yes, it is a problem.
The Problem with Synthetic Yellows
To put it bluntly, you just don’t see the same yellow body color in synthetic diamonds that you do in natural diamonds. Yes, they are both colored by nitrogen, but there’s is something about the yellow body color in a synthetic that looks “different” than the natural diamond.
The Science of Yellow
Thomas Hainschwang, director and owner of the GGTL Laboratory in Lichtenstein, is a world recognized diamond scientist. And like Scarani, an AGA Bonanno Award recipient. When asked for advice regarding using synthetic diamonds in color grading Master Sets, he too was skeptical, not just because of the brownish tint they might display, but also for their unique yellow body color.
According to Hainschwang, “in HPHT synthetics, the yellow color originates from single nitrogen (C-centers) while in ‘cape’ yellow diamonds that are used for master stones, the yellow color is caused by N3-centers. C-center induced yellow color is not identical to N3-center yellow.” says Hainschwang. “Their absorption spectra are very different from each other, and that is precisely the problem with such synthetic reference diamonds. The only synthetic diamonds that could possibly serve as masters are HPHT synthetics as they are always yellow unless the nitrogen intake is limited by the use of a so-called nitrogen-getter.”
“In contrast,” says Hainschwang, “as-grown CVD synthetics are generally brownish in color and not yellowish, hence not at all suitable; only after HPHT treatment CVD synthetics may appear yellowish from C centers, but it would be very hard to find stones that correspond to the lower color grades.”
As Hainschwang points out, “There is no way that you can make a synthetic diamond colored by the N3-center. The HPHT synthetics are Type IIa/IIb to Ib, depending on the presence of boron and/or C-centers. And not even a heavily HPHT annealed synthetic diamond will have enough N3 centers to cause yellow(ish) color. The C-center always dominates.”
In other words, you cannot use synthetics for Masters in the yellow range since they will never look the same as a cape series Type I natural diamond.
The Short List why it Cannot be Done
▻We Cannot find a manufacturer who can supply such an inventory of stones to be examined and sorted for possible Master Sets.
▻Synthetic diamonds can have a brownish tint, and so GIA will not grade them as a Master Stone.
▻Synthetic diamonds have a different yellow appearance than natural diamonds, which will defeat the purpose of the Master Set.
Are we done now?
Let’s Rethink This – Going Hybrid
Not willing to throw in the towel just yet, Scarani took a completely different tack.
What if they kept the high colors—the colorless E, F, and top near-colorless G Master Stones—synthetic (since they wouldn’t have to deal with any yellows and could reject any synthetics with a brownish tint), and used natural diamonds for the H, I, J, K, and L Masters, just as we would in a traditional set? Problem solved?
Scarani reached out to Hainschwang to see what he thought about this idea, using synthetic diamonds only for the top colors. Thomas again was skeptical.
But when Scarani told him about using visual optics instead of spectra, there was a change of heart.
Is This Possible?
“’Thomas, if I’m using my eyes or a device that is using the visual approach, not the spectrum centric approach, do you think this can be done?’”
After a pause, to Scarani’s surprise, the answer came back, “Why not?”
Not relying on Spectroscopy?
With visual optics, notes Scarani, “we are not comparing the spectrum of Type IIa with Type Ia. What we are doing is comparing them by eye.”
This is the key difference from most machine grading systems. These machines are essentially spectrometers, which, while greatly improved in recent years, rely on algorithms to interpret absorption spectra. However, this approach doesn’t work with non-Cape Series diamonds—making it impossible to include synthetic Type IIa diamonds in the set.
Machine visual optics, however, have improved dramatically over the past two decades, to the point where color grading no longer has to depend on a diamond’s chemistry, but is simply graded on how it appears.
So now what was needed, besides a consistent supply of suitable diamonds, was a well-respected professional gemological laboratory, other than GIA (because GIA will not grade synthetics), that uses a color grading machine based on a visual optics approach, rather than spectroscopy.
And because he had already spoken to Sharrie Woodring, senior gemologist at GCAL by Sarine in New York, he was prepared. “I explained to them what we were doing, and asked if that would be possible.” The answer came back, “yes.”
The Green Light!
Scarani was now hopeful. But we still have more problems to solve. Going back to the first and most important step, Scarani needed a reliable source of material, “reliable for both synthetic and natural diamonds,” says Scarani.
Stuller
For more than 50 years, Stuller has been at the heart of the jewelry industry, providing quality supplies to jewelry professionals all around the world. They are the largest supplier of both natural and synthetic diamonds in North America, recognized for their rigorous and comprehensive screening process to verify the origin of each diamond they provide.
Along with that challenge, Stuller had to be all in for the long term.
Talking to Guy Borenstein, Stuller’s Director of Gemstone Procurement and Senior Gemologist, Scarani notes, “I was very, very clear since the first moment I made contact, that this is not something you are selling and then you go away. If you really want to be involved in this, it has to be for the long term.”
Basic Math, It’s Not Affordable
Scarani knows that there will be a lot of work involved in creating Master Sets. This, coupled with the small number of units needed to be produced every year, this simply will not be a money-maker. “What I wanted was formal assurance that this was going to be a service that Stuller would continue to provide, no matter what.”
“I see this as a service,” says Scarani. “I’m not seeing it as a profitable product.” And Stuller has to know this going in. “We all know that this is really not the super economically viable endeavor,” as Scarani states the obvious, “otherwise there would be plenty of companies already doing that.”
The Differences Between HPHT and CVD
“If you are creating a set out of synthetic CVD diamonds, there is no way in the world that you can get rid of the brown or grey tint,” says Borenstein. “But with HPHT, you can get to a point where the colorless and top near colorless (E, F & G color grades range) will look the same as the natural.
“The original idea was to use only HPHT diamonds,” says Borenstein. But first, before they were color graded, the HPHT diamonds were checked for two things: 1. persistent phosphorescence (relatively common in HPHT diamonds), as this could affect the grading, and 2. tested for relative levels of boron using FTIR (Fourier Transform InfraRed spectroscopy). The presence of boron can cause the diamond to appear grey (or even blue).
According to Borenstein, these two simple tests eliminated a huge amount of inventory – 90% of the stones tested! Of the remaining 10%, “a few with undesired tint are rejected. These are sorted out by my gemologists through manual inspection,” says Borenstein.
The “E” Master Problem
Finding the right E color diamond was … what’s the word? … elusive.
For some reason, Borenstein couldn’t find good E color HPHT synthetics. So, how do you solve THAT problem? “For the E color, eventually we chose a CVD synthetic that was HPHT treated,” says Borenstein, “because it didn’t show any tint.” Brilliant! (Sorry – no pun intended. – gr)
E, F, and G Masters…
So, to recap, Stuller will supply synthetics for the colorless and top near colorless color grades – for the E, F, and G Masters.
Grades Below G
“Below G, we decided to use only natural diamonds,” notes Borenstein. You can tell the difference in yellow tint between the lab-grown and the natural diamond even though both are colored by nitrogen (Type I vs. Type II – we talked about that up top with Thomas Hainschwang). “With lab-grown, the color will look ‘funky’ to an experienced grader,” says Borenstein, “and so it’s better to stay with natural diamonds [in the H, I, J, K and L range].
Okay – Finally – We’re all in with supply!
THE MAKING OF A MASTER SET
Step One – Stuller’s Massive Sorting Project
The first phase of creating a Master series of diamonds involves Stuller examining its inventory, sourcing natural and synthetic diamonds through its wide network of vendors.
All CVD and HPHT synthetics will be tested for fluorescence and phosphorescence, and then HPHT synthetic diamonds will be examined using FTIR to look for boron.
The natural diamonds are also screened in FTIR to ensure they are Type Ia diamonds with no hydrogen component (hydrogen can add a grayish tint to the stone). In addition, the stones are tested to ensure that no fluorescence is present.
Then, Stuller’s gemologists visually color grade each diamond, using 2 GIA graded Master Sets, and looking for those diamonds with colors in the highest position of each grade, and that the color distribution is even.
Next, the grading staff takes the cherry-picked candidates and examines their clarity. Only VS2 or better can be accepted as a color grading Master. This also requires having no dark inclusions, clouds, or color graining.
Proportions
All diamonds that have made it through the sorting process up to this point are scanned on the 3D proportion analyzer by OGI to ensure that they fit the proper proportions needed. The digitally collected properties, together with symmetry and polish, are also manually verified by the gemologists’ inspection.
“We do the entire process that you would be doing for finding Master Stones,” notes Borenstein, “but adding a few more steps at the beginning to ensure we are using the right natural and lab-grown diamonds. And only those candidates will then be sent on to the professional lab.”
Can Another Lab Grade to GIA Master Color Standards?
Now with the GIA laboratory unwilling to grade synthetic diamonds for use as Master Stones, Scarani needs a professional diamond grading laboratory that has the capability to grade diamonds as Masters Stones.
With phase one complete at Stuller, it’s now on to phase two – the diamonds that have been pre-sorted by Stuller arrive at GCAL by Sarine.
GCAL by Sarine – Now This is Fascinating!
Sarine is well-known for developing scanning devices used in the gem industry. Sarine Technologies are pioneers in diamond analysis technology, specializing in advanced systems for marking, measuring, and grading, that evaluate rough and cut diamonds, including the Galaxy, Sarine Clarity II, Sarine Color, Advisor (Tenders), Diaexpert, Diamension and more.
Sometime around 2018, Sarine launched what they call Sarine Color, using automated optical analysis and AI to accurately assess the color and fluorescence of a diamond.
Artificial Intelligence
Artificial Intelligence (AI) simply means that the device collects data and uses it to create a database. This database is then used to compare and grade other diamonds with similar appearances to those already in the system.
What sets Sarine Color apart from most other color grading devices is that it’s an optical scanner. “The machines [that other laboratories may use] are spectroscopic based, gathering absorption measurements,” says Angelo Palmieri, president of GCAL by Sarine. “This works really well for Cape yellow stones, but not on browns, greys, diamonds with fluorescence, type II, and other issues.”
Sarine Color’s Database
“Sarine launched this AI based vision system before most people in the world understood what AI was. When we feed it 30,000 D colors, and 30,000 E colors, and 30,000 F colors, and 30,000 G colors, it is recognizing these grades through machine vision and image processing.” And what makes this Master Set project possible is that the more diamonds with GIA color grades are examined by Sarine Color, the more GIA information can be stored for future reference. As Palmieri notes, “It started to learn GIA grading.”
Partnership
GCAL and Sarine have only been partners for the past two years. And what they see is a machine that can continually update and perfect its grading skills.
“Sarine Color truly has the best pulse at any given point in time of GIA’s color grading because there’s constant data going into the systems.” And that real-time data set keeps building. As the machine rotates the diamonds to measure every angle, it is even collecting data for the challenging stones such as fancy shapes and color zoned diamonds.
“There are even different algorithms for natural and lab grown diamonds – a very data intensive process,” says Palmieri. “And we see it work every day.”
Selecting Master Grades
More importantly, the detailed color data from Sarine Color allows GCAL to pinpoint exactly where a diamond falls within its assigned color grade range. Is it a high E, a low E, or a solid E? Sarine Color can even determine how close a color is to the edge of the next color grade.
This is the data necessary to qualify a Master Stone. Without giving away any technological secrets, Palmieri tells us that there’s a number generated by Sarine Color. “It’s within a 10th of a grade,” says Palmieri, “and it’s highly repeatable.” This information, only for laboratory use, helps maintain consistent grading, not just for Master Stones, but for client stones as well.
Staff Gemologists are a Key Component
“Our graders play a pivotal role in this process,” says Palmieri. Even though the machines are repeatable and consistent, Palmieri knows just how important it is for his grading staff to have the final word. The laboratory gemologists and the diamond merchants, retail jewelers, and appraisers all need to see the stones the same way. … “which is why a stone can only be authorized as a Master if the machines and graders agree,” notes Palmieri.
GIA Quality Masters
“Therefore, it is fair to say, that the Master Sets that we’re building, based on the grading database and criteria we have, are very closely aligned to GIA, as they are currently grading color.”
“Our AI technology has the ability to track [color grading] in real time, through the data collection that is ongoing throughout major diamond centers.”
It’s All in the Details
With this exacting data, not only can GCAL approve a Master Stone of a certain grade, but it can potentially assemble matched sets that transition smoothly from one grade to the next.
“It’s a very involved process,” says Palmieri. “Not a simple task. There are very few companies that could do this, to produce highly curated Master Sets through people and machines.”
“The best of both worlds,” exclaims Palmieri. “This provides a cost-effective and accessible solution. It takes a massive number of diamonds to bring this project to scale and there are not many companies like Stuller who could feed a project of this scope. Without their support, we could not proceed to provide the number of sets needed.”
Project Complete!!
Now for the BIG question: How Much?
It’s a Tool – You’re Not Just Buying Diamonds, per se, but a Grading System
“This is a tool,” reiterates Scarani. “You cannot compare this to anything else. Because of what is involved here, it’s a lot of work, of selection, comparison, back and forth, and so on, so the price is not about the price of the diamonds. The price is about the work, the labor, the shipping back and forth…”
“I really hope that they will keep it as affordable as possible. But again, I have no control over that.” The AGA is not making money off this project. This was really just about trying to find a solution to a big problem, members trying to find an affordable set of Master Stones to establish their credentials as an AGA Certified Gemological Laboratory.
“This is a real miracle combination,” says Scarani. “You have someone who has access to synthetic and natural diamonds in these quantities, with the equipment and personnel that can sort hundreds of stones… You have a lab that can create sets using new AI visual grading that is aligned with GIA grading…
It’s a combination of very unique features.”
In the end, this project has been a huge, concerted effort from all parties involved, trying to find an answer to a question that hasn’t been tackled for more than 20 years.
When Hybrid Master Sets are finally available, you will find out from the Accredited Gemologists Association, Stuller, GCAL by Sarine, and right here in the Roskin Gem News Report.
https://accreditedgemologists.org/hybrid-diamond-master-sets/
About the Accredited Gemologists Association (AGA) The Accredited Gemologists Association (AGA) is an esteemed international organization of independent gemologists and industry professionals dedicated to advancing gemological knowledge, ethics, and best practices. Through education, research, and collaboration, AGA supports the highest standards of integrity and expertise in gem evaluation and appraisal.
About Stuller In 1970, Ma hew Stuller founded Stuller Inc. headquartered in Lafayette, Louisiana. The prime manufacturer provides a wide range of goods and services for jewelry professionals worldwide. Stuller’s core product categories include bridal jewelry, wedding bands, fine jewelry, mountings, diamonds, gemstones, findings, metals, tools, packaging, and digital solutions.
About GCAL by Sarine GCAL by Sarine is a globally recognized diamond certification laboratory committed to accuracy, consistency, and consumer confidence. Utilizing advanced AI-driven technology alongside expert human graders, GCAL provides guaranteed diamond certification and innovative solutions to meet the evolving needs of the gem and jewelry industry. Since 2008, GCAL has been annually reaccredited as an ISO Accredited Forensic Laboratory, the only gems and jewelry lab globally to hold such an accreditation and distinction.
