Most retailers insist on getting “certificates” when they buy high-quality diamonds. It’s not unusual, therefore, to see wholesale diamond offices with literally hundreds of these grading reports stacked up in the safe. A seal of approval from the Gemological Institute of America’s Gem Trade Lab (GTL), Diamond High Council (HRD), International Gemological Institute (IGI), European Gem Lab (EGL), or American Gem Society (AGS) carries considerable weight.

At more than $100 apiece, these papers represent a substantial investment. “Clean” papers, those with no comments or unusual grades, facilitate a diamond sale. They assure the retailer of a stone’s quality and justify the wholesaler’s asking price.

But when additional or unusual comments draw attention to a diamond’s inclusions or proportions, the certificate becomes a risk. These comments reduce the value of the diamond, which in turn may kill the sale. The more you know about certificate comments, the better you’ll be able to explain to the customer the reasons behind them. A satisfactory explanation may well salvage the sale.

What the comments mean. Most reports include comments in the lower section, below the listing of the gem’s weight, proportions, finish, clarity, and color grades. Grading laboratories confine most comments to proportion details or to inclusions that, if plotted on the diagram, would misrepresent the diamond’s internal characteristics.

Seemingly innocuous comments such as “surface graining not shown” or “internal graining not shown” are purely identification features that are almost never drawn on the diagram. Other comments, such as “additional clouds are not shown” or “pinpoints are not shown,” are simply designed to lessen the grader’s workload.

“ ‘Pinpoints are not shown’ is not an issue, but it certainly is a negative-sounding comment,” says Barry Rogoff, diamond cutter of Ideal-make stones in Los Angeles. “It’s not the devil people seem to make it.”

When that’s the only comment, he’s right. But several of these apparently inconsequential comments can be deadly. “You don’t want to see three or more comments all together,” says Shannon Eichner of Aronow & Ross diamond wholesalers, also in Los Angeles.

Certain comments, however, can undermine a certificate even in the absence of other items. The four most fatal of these pertain to high or shallow crown angles.

“Crown angles are greater than 35°” is the most common of the four. This and three other comments – “crown angles are greater than 40°,” “crown angles are less than 30°,” and “crown angles are less than 25°” – criticize the diamond’s proportions and leave the wholesaler with a lot of explaining (and perhaps discounting) to do.

According to Marcel Tol- kowsky, creator of the Ideal proportions, the greatest dispersion released from a diamond occurs when the crown angles are at 341/2° from the girdle plane. Some believe that citing a 36° crown angle is splitting hairs. Says Rogoff, “I think they should keep the comment of ‘greater than 40°,’ but when it is only a degree and a half [above Tolkowsky], that’s a little tough.”

A certificate that lists crown angles of “greater than 35°” tells the buyer that he’s paying for more weight that isn’t visible when the stone is face-up (a taller crown as opposed to a wider circumference). The comment “crown angles are greater than 35°” also implies that, as some have theoretically predicted, the diamond with crown angles of 36° or more would look less brilliant than one with 34 1/2° angles.

With such little angle difference, the two diamonds may well look the same to the human eye. It’s also quite possible that a diamond with crown angles of 36° or more will show more dispersion and appear “better” to some, but you wouldn’t read that from the comment. So much depends on the rest of the gem’s proportions. “On some stones, the crown angle really makes a difference,” says Lou Pearl, president of L.P. Diamond & Gem Company in Los Angeles. “On other stones, it doesn’t.”

Is it worth mentioning? There are two schools of thought about how much information belongs on a certificate. Some prefer more, others less.

“I don’t personally agree with [those who prefer to provide] less information,” says Jeffrey Fischer, president of Fischer Diamonds in New York as well as the Diamond Manufacturers and Importers Association (DMIA). “But negative comments on a technicality [such as ‘crown angles greater than 35°’] are not productive.”

When it comes to certifying diamonds, Fischer believes that dealers rely too much on the proportions and grades listed on diamond grading reports and not enough on how the stone actually looks. “We keep trying to quantify [beauty],” says Fischer. “You cannot always tell what the diamond looks like by just simply looking at the report.”

When a diamond receives a comment referring to obvious crown angle height – greater than 40°, for example – that comment certainly bears mentioning. “But when you have one with a 35° angle comment, you need to put the diamond on a ProportionScope to see why the comment was made,” says Fischer. Like many dealers, he questions the criteria by which graders elect to issue comments. Ultimately, it comes down to aesthetics. What matters is, “Is it a beautiful diamond or not?” says Fischer.

Steep and shallow crown angles. If a crown angle that’s merely 11/2° above Tolkowsky’s “ideal” occasions a comment from GIA and other like-minded labs, why is there more leeway on the shallow end? That is, why must a crown angle be at least 51/2° below Tolkowsky (29° or less) before it’s worth mentioning? According to Tom Yonelunas, CEO of GIA’s Gem Trade Lab, a comment about a shallow measurement implies different consequences from a comment citing a steeper angle. Diamonds with crown angles over 35° tend to lose their brilliance, or, as Yonelunas says, “start to show darkness.”

Labs like GIA’s now use the Sarin laser measuring device to gauge exact angles, rather than the approximations obtained from the old workhorse, the less-precise ProportionScope.

With higher crown angles, diamonds also look “old.” “You may have even heard that they appear lumpy,” says Yonelunas. But that’s just a subjective observation. Scientifically, it has been confirmed that higher crown angles diminish the brilliance. That report will soon be published in Gems & Gemology.

Says Yonelunas, “Our research study will show that both brilliance and fire are mainly affected by a complex interrelationship of crown angle, pavilion angle, and table size. It’s showing that beyond that point [36°], when a traditional pavilion angle is maintained, we were correct. It’s validating what we had already observed.”

On the other hand, when crown angles are lower than

341/2° and the traditional pavilion angle is maintained, there’s no appreciable difference in brilliance. “It’s now a durability concern,” says Yonelunas. Excessive pressure at the girdle edge can break the stone.

Coming clean. Comments or other unusual calls on a certificate almost inevitably require explanations. Yet most clients view such explanations with suspicion, as a presumed drawback that may well stifle a sale – even if the explanation is in fact a positive one. Jewelers would much rather avoid having to decipher a comment for a customer in the midst of a sales presentation.

For example, an isolated comment such as “additional clouds are not shown” may not blow the sale, but it’s certainly not self-explanatory. While the comment is gemologically correct, retail customers tend to think of translucent-to-opaque white “clouds,” which of course is not what you have inside the diamond. “[They] think of cumulus clouds, rain storms,” laments Pearl.

In that case, you need to explain what the comment really means and possibly consult an inclusion book or make use of a microscope. This ought to diminish the inflated importance the comment has attributed to an otherwise insignificant inclusion.

Crown angle comments are another matter. Never discuss the facts of a crown angle comment without first considering the rest of the diamond’s proportions and then actually looking at the gem. Otherwise, you’ll be conceding that the diamond looks less than perfect. After all, the customer might wonder, why would there be a comment if something were not amiss?

Some consider dispersion to depend solely on crown angles, but in fact it’s also a function of the pavilion angles. Only by knowing all the proportion measurements, or actually measuring dispersion and light return and then looking at the diamond, will you be able to determine if the crown angles have affected the gem’s beauty.

Playing the odds. Many dealers spend time and money recutting diamonds to eliminate crown angle comments. If the diamond has enough weight to be repolished and stay above a particular price-break category on wholesale price lists, then the stone goes back on the polishing wheel.

Changing the crown angles avoids any discussion about make and any comparisons to stones with no-comment certificates. It thereby helps solidify the asking price and obviates the need to discount. Of course, repolishing to reduce crown angles usually means more than just a few points in weight loss, since you’re polishing a number of bezel and star facets.

You also need to consider the danger involved in recutting diamonds. Whenever a stone is repolished, there’s always a risk it might chip or break in the recutting process. Rarely though this may occur, there have been stones that have shattered on the wheel during even minor repolishing. Still, if you have a good cutter, the odds are that you will win, keeping the stone intact and eliminating the crown angle comments. Any way you look at it, selling diamonds with certificates is a tricky business.

What about fluorescence? Although it isn’t in the comments section of a grading report, the fluorescence call can also be a cert killer. And even though GIA issued a report that downplays the significance of fluorescence in its Winter 1997 Gems & Gemology issue (JCK, September 1998, p. 146), the trade is slow to take up the flag.

For the last two decades, retail and wholesale diamond merchants have claimed that fluorescence detracts from the beauty of a diamond. Before that, however, fluorescence was considered a positive characteristic. Historically, diamond merchants referred to blue fluorescent diamonds as “blue-white,” and graders made comments on certificates such as “due to the fluorescent nature of this diamond, the color is enhanced in daylight.” Both responses stemmed from the fact that the stone fluoresced blue in daylight and supposedly looked better.

GIA’s recent study reveals that this notion is incorrect. In fact, fluorescence has little visible effect at all. And yet one of the quickest sale killers is to have “strong blue” or “very strong blue” or any strength of yellow fluorescence noted on the certificate. “I even have clients reject medium blue,” remarks Eichner.

Explain it or lose it. Comments on a report should tell you where to focus your attention in the sales presentation. Does this particular characteristic affect the diamond’s beauty or durability? After all, the comments are there for a reason. How significant is the comment relative to the salability of the diamond?

If the comments mention graining or an inclusion not plotted on the diagram, you should be able to locate it and show or describe it to the customer. Also determine why it was mentioned but not plotted and try to gauge its importance as an identifying feature.

If the comments concern crown angle analysis, you should be familiar with the effect of crown angles on brilliance and dispersion, describe what the customer should see, and determine whether or not the beauty of the stone has been affected. Also be sure to examine pavilion depth and table size; according to the not-yet-released GIA study, these factors can affect how light is finally transmitted through the crown facets.

It’s always difficult to sell a diamond when the certificate has an unusual comment. It comes down to what you know and how well you can explain the comment to your customer.

“When you put two stones side by side, one with [a comment on the certificate] and the other without, the value of the one that has the comment drops dramatically,” says Pearl. If you can’t provide a convincing explanation, that comment, however innocuous it may be, could well be a deal-killer.

“You cannot always tell what the diamond looks like by just simply looking at the report.” – Jeffrey Fischer, Diamond Manufacturers and Importers Association

The comments section of GIA’s Gem Trade Lab (GTL) Diamond Grading Report, located below the fluorescence notation, is used specifically for crown angle deviations, details of finish, or inclusions that are not plotted on the diamond diagram.