about Fancy yellow diamond grading
Diamond Grading – Clarity
The clarity of a diamond is determined by the number, location and type of inclusions it contains. Inclusions can be microscopic cracks, mineral deposits or external markings. Clarity is rated using a scale which contains a combination of letters and numbers to signify the amount and type of inclusions. This scale ranges from FL to I3, FL being Flawless and the most valuable.
The process of the growth and creation of a diamond inside the earth does not occur evenly, but in several phases. In each phase, the conditions such as temperature, pressure and cooling are not the same and do not always remain constant. As a result, most diamonds contain what are called inclusions, internal features caused by the constantly changing conditions during different phases of the diamond’s creation. These inclusions come in many forms including cloud-like features, fracture or tension cracks or even enclosed minerals that were present during the growth process of the diamond.
The GIA (Gemological Institute of America) has designated that clarity of diamonds is graded under the following guidelines:
FL: Diamond free from internal and external flaws under 10X magnification.
IF: Absolutely free from internal faults fewer than 10 X magnifications. May contain external features that should be so small that they can easily be removed by polishing.
VVS1: Very, very small inclusions in the stone, very difficult to recognize fewer than 10X magnification. These inclusions can not be in the field of the table.
VVS2: Very, very small inclusions anywhere in the stone, only smallest external defects allowed.
VS1: Only the smallest inclusions are allowable in the field of the table and only small faults elsewhere in the stone.
VS2: Very small internal faults. Small external defects.
SI1: Small internal faults, not visible to the naked eye.
SI2: Small, easily seen inclusions under magnification in the table, but still not visible to the naked eye.
I1: Inclusions easily seen under magnification, but difficult to see with the naked eye. Inclusions do not influence brilliance.
I2: Large and numerous inclusions, just barely visible to the naked eye through the crown. Inclusions slightly diminish brilliance.
I3: Large and numerous inclusions, easily visible to the naked eye, demising brilliance.
Diamond Grading – Carat Weight
In addition to color, clarity and cut, weight provides a further basis in the valuation of a diamond. The weight of diamonds, and all other gemstones, is measured in carats. Smaller diamonds are more readily available than larger ones, which results in higher values based on weight.
The weight or overall size of a diamond is measured in carats. In fact, all gemstones are measured in this fashion. Of course, the larger the diamond, the more you can expect to pay for it, however the price does not increase on an even scale. A 2 carat diamond will not be twice the cost of a 1 carat diamond, despite being twice the size. The larger the diamond, the rarer it becomes and as such the price increases exponentially.
When choosing a diamond for yourself or someone else, keep in mind that the same size diamond can look bigger depending on the type of setting it is mounted in. Also, a 1 carat stone will look bigger on a person with a size 6 finger, than it will on a person with a size 8 finger.
Diamond Grading – Table Width
Table width is quoted as a percentage of the average width of the diamond’s girdle. Table size is less critical to the beauty of a diamond than variations in the crown and especially pavilion angle. AGS and Gina’s new systems each have top grades that include 61% table sizes.
Yields from most rough diamonds are improved by polishing larger table sizes than we might prefer. Small variances in crown and pavilion angles cause less problems if table sizes are in the range of 55% to 58%.
Larger table diamonds have a better “spread” and can be brighter, i.e. they return more light, but are often less fiery than diamonds with smaller tables. They often have less scintillation. Larger table sizes are considered to be an advantage in smaller diamonds below .10 ct.
Diamond Grading – Total Depth
The total depth percentage is a very important element of a diamond’s proportions and it is greatly responsible for the amount of brilliance that a diamond will display. Diamonds which have ideal to very fine cut with proper total depth percentage provide the greatest brilliance.
Ideal to Very Fine Cut Diamonds have total depth percentages between 59% and 63%. Diamonds within this range usually provide excellent brilliance. Diamonds that have depths outside these ranges usually cost less, but a degree of brilliance is lost. When depth percentage becomes greater than 65%, the center of the diamond becomes dark as light refracts through the bottom of the diamond.
However, proper total depth percentage does not guarantee proper cut. Total depth percentage is very important but it can sometimes be misleading. Total depth percentage is a representation of a diamond’s overall total depth. It is possible for two diamonds to have the same depth percentage and be proportioned differently.
Total depth percentage is a combination of many other important elements of diamond cut. These elements include crown height, crown angle, pavilion depth percentage, pavilion angle and girdle thickness. These elements are properly proportioned in ideal cut diamonds.
However, some diamonds with total depth percentages that are in the range of ideal may be improperly cut and display less brilliance. A diamond with ideal total depth percentage may also have an overly deep bottom, (deep pavilion depth percentage & steep pavilion angles) and have a very low top, (low crown height & shallow crown angle.) A simpler example would be two men that are six feet tall. One man has perfect symmetry. His upper body is in proper proportion to his lower body. The other man has very long legs and a short waist.
Diamond Grading – Pavilion
The point on the bottom of a diamond’s pavilion is called a culet. During the manufacturing process, the culet is often polished as a flat facet so that it does not get chipped. These days the cutter usually ‘closes’ this facet to a point, but sometimes it remains as a small extra facet; this is not so bad because it protects the culet from chipping as the diamond is handled and while the jeweler is setting the stone. In some cases, you will read that a round brilliant cut has 57 facets, and sometimes 58; the 58th facet is the culet.
A diamond behaves as a window if opposing facets are parallel, and this is exactly what happens if the culet is too big, because the culet is parallel to the table. The result is that you can see right out the ‘whole’ the culet appears to make in the center bottom of the diamond. If you have ever seen a large, old cut diamond, this will be apparent.
The culet size is listed on a grading certificate and your diamond’s culet should be pointed (no culet), very small, small or medium because these are not visible to the naked eye.
Large to extremely large culets may be visible to the naked eye and can look like an inclusion.
Diamond Grading – Fluorescence
Roughly one third of diamonds available in the market fluoresce, like the fluorescent minerals you have seen in natural history museums, or the novelty shop toys under the black (UV) light. The effect is like a white shirt in a nightclub.
Fluor can be faint to very strong, and the most common fluorescent color is blue. As blue is the complimentary color to yellow, the most common tinted color in diamonds, blue fluorescence can make yellowish diamonds look white or colorless.
A GIA survey found that fluorescent diamonds were favored over non flour stones, especially in lower colors, but even in the higher colors (D, E and F) which are often discounted by the trade. Many years ago colorless fluorescent diamonds were highly prized and referred to as “blue-white”. But sales people used the term too loosely for any diamond with fluorescence; “blue-white” usage was outlawed by US trade practices laws.
One “for” argument for discounting fluorescent diamonds is because the GIA lab grading lights emit a small amount of ultra violet light; fluorescent diamonds might be assigned a better color grade. The ‘against’ argument, although the GIA Gem Trade Lab has not openly discussed the issue, is that UV light is almost always present in viewing environments, so why not grade color in realistic lighting?
But the most likely reason for flour diamond discounting is because of the sad fact that many jewelry salespeople are not able to explain complex phenomena like flour; a Fluor (or any comments) written on a report makes the diamond harder to sell = worth less!
Some diamonds have extremely strong fluorescence and appear oily or cloudy. This is BAD. But the GIA study found them to be very rare; they were unable to find enough cloudy stones from the 26,010 samples they used.
Rarely diamonds fluoresce another color like yellow or orange. Do not buy them unless the diamond concerned is a fancy color of the same hue as the fluorescence (which will make it more intense). White diamonds with yellow or orange flour will appear to be a lower color when seen in light with a UV component.
When the UV light is turned off, fluorescence ceases instantly, but some stones continue to phosphoresce for a little while.
Diamond Grading – Polish
Polish is graded the same way as symmetry: Excellent, Very Good, Good, Fair or Poor on a GIA report. Poorly polished facets may reduce the intensity of light reflected from, or refracted into and out of, a diamond. Labs assess polish by examining the diamond, facet by facet, with reflected light under a microscope.
The market has read more into Polish (and symmetry) simply because it is there on the report and because GIA has no cut grade standard. A common polish defect is surface grain lines. Even the most skilled cutter can encounter variations in hardness or grain, just like in wood, as they polish a facet. The result is a microscopic polish line running across a facet. These grain lines are very common in pink fancy colored diamonds, but often they can only be seen in reflected light.
If you choose a diamond with an SI or VS inclusions, a few microscopic polish lines may be of no relevance. But if you were considering buying a Flawless diamond, then excellent polish could be a major consideration.
If the polish is rated as fair or poor, visual performance may be noticeably reduced.
Diamond Grading – Symmetry
Symmetry is graded as Excellent, Very Good, Good, Fair or Poor on a GIA report. When polishing a rough diamond, the aim is to cut the heaviest, most valuable diamond possible. This often means polishing a diamond with imperfect symmetry to avoid inclusions or just leaving more weight to achieve an even carat weight, such as 1.00 ct. The polished diamond may be slightly off round, have variations in girdle thickness, tilting of the table, and off centering of the table or the culet.
Very few diamonds are perfectly symmetrical, but symmetry is less important to the overall beauty of a diamond than the critical facet proportions. You may never notice any difference between diamonds with excellent or ideal and very good or good symmetry.
Fancy Yellow Diamond Grading
In your search for diamonds, you may come across “fancy color” diamonds. The most prevalent fancy color diamonds are Fancy Yellow. There are several color grades that can be assigned to a Fancy Yellow diamond and the differences can be a bit confusing. The chart below should help illustrate the differences. Please note that the colors you see are not an exact representation as different monitors display colors differently.
In Japan in the late 1980’s someone noticed a hearts pattern when looking at the back of a diamond through a Firescope™– the Hearts & Arrow’s viewer was born, and diamonds with H&A’s patterns became very popular in Japan. In the mid 90’s H&A’s arrived in USA.
From the top, a diamond shows an arrows pattern and when flipped over to the pavilion side you see 8 hearts with small ‘V’ shapes. A true H&A’s has the patterns visible at a single glance indicating the diamond has optically perfect symmetry. When buying H&A’s online the only way you be sure the diamond is a true H&A’s is to see actual photos of the stone as there are few grading standards for H&A’s. Some wholesale dealer’s version of H&A’s can be rather chaotic.
Only some Japanese labs, HRD and IGI grade the quality of the H&A’s patterns. The most popular labs with many Pricescope forum members – AGS and GIA – do not grade H&A’s. Be aware that GIA and some other labs note on grading reports that there is a Laser Inscription of “H & A” on the diamonds girdle. This is not a grading of H&A’s – they are simply reporting the inscription on the diamond.
Diamonds with H&A patterns are frequently among those with top performance. However there is no proof yet that the absence of H&A optical symmetry (or any other type of pattern) means that a diamond will have lesser performance, as it’s the overall geometry of a diamond that determines its light performance. It is possible to produce H&A diamonds with inferior performance and some experts suggest diamonds over 10ct should probably not be cut to show H&A’s patterns. H&A viewers can help you identify the level of optical symmetry in a diamond, but not its performance. We urge you to compare all diamonds in different lightings (not just bright jewelry store lights) and use other methods and tools to look for legitimate proof of performance when making your purchasing decisions.
Some brands of H&A’s, like Hearts on Fire® have been very successful in retail stores, and there are also several online brands, one is Brain Gavin’s who wrote this detailed article.
Table Size »
Ideal Cut to be challenged…
The ideal cut diamond has remained the undisputed “king of cut” in the diamond world for decades. It has long been heralded for its ideal balance of maximum reflection and dispersion. However, in the last twenty years or so, some ideal manufacturers began to drift away from the strict proportions prescribed by Marcel Stokowski. The reasons for this evolution revolve around yield (trying to get a diamond with more carat weight), big price jumps between size categories i.e., .69-.70 ct., .89-.90 ct., .99-1.00 ct., etc. and the spiraling cost of rough diamonds. Strict proportions limits were compromised and table size percentages grew to 57% maximum from the 53% of Stokowski. Perfect polish and symmetry became less important.
Economics takes precedence over perfection.
As cutters deviated from the strict Stokowski specs their diamonds lost some of there potential for perfection. Ideal cut became what it is today… an ideal range of specifications known as the American Brilliant Cut.
Major American manufacturers of ideal cut diamonds began to manufacture in lower wages countries in search of low production costs. These diamonds once fashioned one by one, with the utmost of care, were mass produced in large factories. Stones cut on automated equipment often receive little individual attention. Their automatic machines were set to produce hundreds of diamonds a week in the ideal range. As a result, some became perfect ideal cuts with top polish and symmetry. Still others barely made the grade; their polish and symmetry only disappointingly average. Fortunately, not all cutters followed this trend and some continued to turn out superior ideal cut diamonds. They realize the beauty comes from finishing the job.
Today, ideal cut diamonds still reign far above average cut diamonds in both beauty and rarity. Like the finest wines or a luxury car, ideal cut diamonds are not for everybody. Knowledgeable buyers of quality still seek out ideal cut diamonds in their quest for “the best money can buy”. That quest is about to become more interesting with the introduction of the newly crowned king of cut. The new “super ideal” cut… the hearts and arrows ideal.
Hearts and Arrows Cut Takes “Ideal Cut”
to a Higher Level
In the early 90’s, in Japan, ideal cut diamonds were all the rage. In this country, the second biggest diamond market, where quality, status and brand names are in vogue consumers became big buyers of ideal cuts. Cut grades of “Excellent”, “Super Excellent”, and “Triple Excellent” were much sought after. Ideal cuts with these grades were known to show the “Cupid effect“, or a visual pattern of 8 hearts while looking down through the pavilion and 8 arrows when viewing the stone in the table up position. A special magnifying viewer is used to show these phenomena. These diamonds become known in the trade as “hearts and arrows”.
Hearts and arrows viewers, like the one shown here, were developed in Japan for use across the retail counter to show consumers this unique phenomenon
Cut Grades Imported to America!
American Gem Society (AGS) Laboratory issues cut grades on grading reports based on measurements provided by Saran Dia-mension technology. This is the first major American laboratory to use a numerical system for assessing an overall cut grade. The lab grades seven main components of cut (including polish and symmetry) and applies them to a deduction chart with grades from 0 to 10. The top grade is 0 Ideal (no deductions), 1 Excellent (almost ideal), and so on down to 10 Poor. Though they have considered it, the AGS lab currently has no plans to include hearts and arrows comments or photos in their reports. The terms 0 Ideal, zero cut, triple zero, and AGS 0 have become buzz words in the trade for ideal cut diamonds. Not all ideal cuts are hearts and arrows… remember we call them “super ideals”.
Polish and Symmetry should be Exceptional
Ideal cut diamonds are cut to widely accepted proportions and angles, however, sometimes the cutter does not spend the extra time finishing the stone in ideal fashion. Finish includes reaching the degree to which the finish of the surface approaches optical perfection. A well polished diamond shows no polish lines or other surface blemishes under 10 x magnifications. Finish also addresses the symmetry of the stone which includes the exactness of placement and shaping of opposing facets and other portions of a finished diamond. Symmetry is judged on the basis of the degree to which the shaping and placement of facets yield exact mirror images of opposite features. The hearts and arrows pattern is only possible when exceptional symmetry exists. As mentioned before, hearts and arrows diamonds are “super symmetry ideal cuts”.
Time and money…is a big consideration in the diamond manufacturing business. As outlined before, diamonds cut to ideal proportions cost more. If you are not prepared to compensate the cutter for (painstakingly) grinding away valuable rough material… doesn’t buy an ideal cut diamond. Less than 1% of all diamonds become ideal cuts. Hearts and arrows are exceedingly rare, as even fewer are cut to this new higher standard.
Hearts and arrows are not for everyone.
This web site was designed to be an invaluable tool to instruct the discerning buyer about the merits of buying cut. There is a lot of good information on the Web regarding color, clarity and carat weight. Unfortunately, there is much misinformation about diamond cutting and specifically what constitutes an ideal cut.
Caveat emptor
As they gain in popularity, many sellers will call any above average cut “an ideal cut”. Now you know…don’t take a sellers word for it. Ask for proof. If the diamond has a certificate (most high quality stones do) ask for a print out from a Saran Dia-mension machine using AGS or AGL software. Only AGS- O or AGL- Excellent are acceptable.
Note: the AGL (Associated Gemological Laboratories of Japan) Excellent grade allows 58% tables. Most American ideal cut sellers include table sizes from 53% to 57 ½% only. These precise measurements should be generated by computerized measuring devices such as the Saran Dia-mension or similar. Though possible to measure by hand using a proportion scope, all major labs use the automatic machines as they are more accurate and repeatable.
GIA Report on a Hearts and Arrows Ideal Cut
Note: excellent polish and excellent symmetry
Gem of the Net
The AGS report shown below is an actual hearts and arrows ideal cut diamond available for purchase from one of our dealers in the United States.
For a dealer in your area please e-mail us to see this or other incredible examples of the world’s finest diamond cutting.
Most labs grade Symmetry as Excellent, Very Good, Good, Fair or Poor on a GIA report. The basis of lab grading includes microscopic examination to ensure that facets meet perfectly; this can result in very different results to the optical symmetry that we have discussed in this tutorial. During the Gina’s 70,000 observation study, diamonds with ‘Good’ symmetry, but proportions that would have qualified them for the top category, were generally not preferred by both trade & consumers survey participants. That is why GIA have decided to allow diamonds to be in a cut grade above its Symmetry or Polish. However AGS insist that diamonds that receive its top cut grade, AGS 0, have Ideal Symmetry (‘Ideal’ which is meant to be a level above GIA Excellent).
When polishing a rough diamond the aim is to cut the heaviest, most valuable diamond possible. This often means polishing a diamond with imperfect symmetry to avoid inclusions or just to achieve a “magic weight” (like 1.00ct). The polished diamond may be slightly off round, have variations in girdle thickness, tilting of the table, and off centering the table or the culet etc. Contrary to popular belief, symmetry defects in a diamond are often the result of a highly skilled cutter, rather than an indication of poor skills.
The diamond images we have used in this tutorial are mostly symmetrical. But in the real world very few diamonds are perfectly symmetrical, but symmetry is less important to the overall beauty of a diamond than the critical facet proportions. You may never notice any difference between diamonds with Ideal, Excellent Very Good or even some Good symmetry diamonds.
Price difference for Round diamonds | |
Polish & Symmetry | % Price difference |
Ex/Ex or Id/Id | 0% |
Ex/VG or Id/VG | -6.5% |
VG/VG | -8.3% |
VG/G | -9.8% |
G/G | -11.6% |