Today, few fine diamonds over one carat are sold without a diamond grading report, or certificate as they are also known, from a reputable laboratory. Reports issued by the GIA/Gem Trade Laboratory are most commonly used in the United States and many countries around the world.
A valuation report not only clarifies the stone’s authenticity, it fully describes the stone and assesses each of the critical factors that affect its quality, beauty and value. Appraisal reports can be very useful for a number of reasons. The information it contains can verify the “facts” represented by the seller and enable a more confident decision to be made when purchasing a diamond. Another important function of reports is to be able to verify the identity of a particular diamond at a later date, for example if it is no longer in their possession for some reason. For insurance reasons, the information Edelstein provided in the report helps ensure that a lost or stolen diamond is replaced with a genuinely ‘compatible quality’ diamond.
Reports are not required for every diamond, and many beautiful diamonds used in jewelry are sold without them. However, if you are considering purchasing a very fine diamond weighing one carat or more, we strongly recommend that you include a report with the diamond, even if it means a diamond has to be removed from its setting (no reputable lab produces a report of a mounted diamond). diamond) and then reset. If you’re considering a diamond without an appraisal, it’s easy for your jeweler to obtain one. Or you can submit a diamond to GIA yourself now that GIA is releasing diamond grading reports to the public.
Don’t rely on the report alone
The availability and widespread use of diamond grading reports, if properly understood, can enable even non-professional individuals to make valid comparisons between multiple stones and thus make more informed purchasing decisions. Reports can be an important tool to help you understand differences that affect price. But we must warn you not to get caught up in what you like or really want. Remember that some diamonds are very beautiful even though they don’t conform to established standards. Finally, use your own eyes and ask yourself how you like the stone.
A customer trying to decide between several diamonds. Her husband wanted to buy her the stone with the best appraisal, but she preferred another stone that was not as good according to the appraisal. They decide against the best diamond and buy the one that made them the happiest. Importantly, they knew exactly what they were buying and paid a reasonable price for that specific combination of quality factors. In other words, they made an informed decision. The reports gave them certainty about the facts and greater confidence that they knew what they were really comparing.
Improper use of reports can lead to costly mistakes
As important as diamond grading reports can be, they can also be misused, leading to wrong conclusions and costly mistakes. The key to being able to rely on a diamond report and have confidence in your decision is knowing how to read it properly. For example, when buyers are trying to decide between two diamonds using diamond grading reports, all too often they make a decision by only comparing two factors that were graded on the reports, color and clarity, and think they made an educated decision. This is rarely the case. No one can make an informed decision based on color and clarity alone. In fact, when there is a significant price difference between two stones of the same color and clarity as the more expensive stone, it is often not the better value. The same color and clarity is only part of the overall picture. Differences in price indicate differences in quality, differences that you may not see or understand. With round diamonds, the information you need is in the report, but you need to understand what all the information means before you can make any valid comparisons.
A word of caution: Do not make a purchase relying solely on a report without ensuring that the report matches the diamond and that the diamond is still in the same condition as described. Always consult a professional gemologist, appraiser gemologist or gemstone testing laboratory to confirm that the accompanying stone report is in fact the stone described there and that the stone is still in the same condition as stated on the report. There are cases where a report was accidentally sent with the wrong stone. And in some cases, it’s deliberate fraud.
How to read a diamond grading report
Check the issue date. It is very important to check the date on the report. It is always possible that the diamond has been damaged since the report was issued. This sometimes occurs with diamonds sold at auction. Because diamonds can chip or break with wear, they always need to be inspected. For example, you may see a diamond accompanied by a report describing it as D – Flawless. However, if this stone were badly chipped after the report was issued, the clarity level could easily fall to VVS and in some cases much lower. Needless to say, in such a case the value would be dramatically reduced.
Who created the report? Check the name of the laboratory issuing the report. Is the report from a well-known and reputable laboratory? Otherwise, the information in the report may not be reliable. Several reputable laboratories issue reports on diamonds. Among the best known in the United States are the Gemological Institute of America Gem Trade Laboratory (GIA/GTL or GIA) and the American Gemological Laboratories (AGL). Among the reputable European laboratories that issue reports is the Belgian Diamond High Council (HRD). Whichever report you read, they all contain similar information, including:
identity of the stone. This confirms that the stone is a diamond. Some diamond reports do not make a specific statement of identity as they are called diamond reports and are only issued for genuine diamonds. If the report is not labeled “Diamond Appraisal Report” there must be a statement certifying that the diamond is genuine.
Weight. The exact carat weight must be specified.
Dimensions. Each diamond, whatever its shape, should be measured and the dimensions recorded for identification purposes, particularly for insurance/identification purposes. The dimensions given on a diamond appraisal are very pricey and provide information that is important for a number of reasons. First, the dimensions can help you determine that the diamond being examined is in fact the same diamond described in the report, as the chances of having two diamonds with the exact same carat weight and millimeter dimensions are slim. Second, if the diamond has been damaged and recut since the report was issued, the millimeter measurements can give an indication that something has been altered, which could also affect the carat weight. Any discrepancy between the dimensions you or your jeweler get by measuring the stone and those given in the report should be a warning sign to examine the stone very carefully.
Finally, the measurements on the report also tell you whether the stone is round or not. Out-of-round diamonds sell for less than perfectly round diamonds.
Fine diamonds are “round”.
The roundness of the diamond affects value and is therefore determined very carefully by the diameter of the stone, which is measured at several points around the perimeter. For a round diamond, the report usually gives two diameters, measured in millimeters and recorded to hundredths: for example 6.51 instead of 6.5; or 6.07 instead of 6.0. These indicate the largest and smallest diameter. Diamonds are very rarely perfectly round, which is why most diamond reports show two measurements. Given the rarity of truly round diamonds, some deviation is allowable and the stone is not considered “out of round” unless it deviates by more than the established norm, approximately 0.10 millimeters for a 1 carat stone . For a one carat diamond, if the difference is 0.10 or less, the stone is considered “round”. If the difference is greater, it is “out of round”.
To calculate an acceptable deviation for a particular stone, average the high and low diameter dimensions given and multiply that number by 0.0154. For example, if the given dimensions are 8.20 x 8.31, the average diameter is 8.25 ((8.20 + 8.31)/2). Multiply 8.25 by 0.0154 = 0.127. This is the acceptable deviation allowed for this stone (between 0.12 and 0.13). The actual deviation in this example would be 0.11 (8.31 – 8.20), well within tolerance for this diamond to be considered “round”. For diamonds over two carats, some flexibility is allowed.
Depending on the degree of out-of-roundness (how much it deviates from perfect roundness), the price can be influenced. The larger the deviation, the lower the price should be.
Dimensions for fancy shapes
Whilst dimensions are not as important for fancy shaped diamonds as they are for round diamonds, there are length to width ratios that are considered “normal” and discrepancies may result in price discounts. The following reflect acceptable ranges:
- Pear Shape: 1.50:1 to 1.75:1
- Marquise: 1.75:1 to 2.25:1
- Emerald form: 1.50:1 to 1.75:1
- Oval shape: 1.50:1 to 1.75:1
To better understand what this means, let’s look at a marquise diamond as an example. If his report were 15 millimeters long and 10 millimeters wide, the length to width ratio would be 15 to 10, or 1.5:1. This would be acceptable. However, if the dimensions were 30mm long and 10mm wide, the ratio would be 30 to 10, or 3:1. This would not be acceptable; The ratio is too large, and the result is a stone that looks far too long for its width. Note: A long marquise isn’t necessarily a bad thing, and some people prefer a longer shape, but it’s important to understand that such stones should sell for less than regular length ones. Always keep in mind the length to width ratio of fancy cuts and adjust the price that is not within the acceptable range.
Evaluate the dosage from the report
As previously mentioned, good proportions are just as important for diamonds as it is for the man or woman who wears them! The proportioning, particularly the depth percentage and table percentage, will determine how brilliance and fire the stone will have.
The proportion information contained in diamond reports is critical for round brilliant diamonds. Unfortunately, it’s of little use for fancy fancy shape diamonds. For fantasies, you must learn to rely on your eye to determine whether or not the proportioning is acceptable: are there differences in brilliance across the stone? Or flatness? Or dark spots like “flies” caused by poor proportioning.
Evaluating a diamond’s proportions is just as important as evaluating its color and clarity grades. Diamonds cut close to “ideal” proportions, “excellent” manufacture stones can easily cost more than the norm, while poorly manufactured diamonds sell for less; very ill-proportioned stones should cost much less. The information in a diamond report can help you evaluate the proportions and know whether or not you should pay more or less for a particular diamond.
Depth percentage and table percentage are the key to beauty
To determine whether or not a round stone’s proportioning, so crucial to its beauty, is good, look at the section of the report that describes Depth Percentage and Table Percentage. The depth percentage represents the depth of the stone, the distance from the table to the culet, as a percentage of the width of the stone. Table percentage represents the width of the table as a percentage of the width of the entire stone. These numbers indicate how well a round stone has been cut in relation to its proportions and must conform to very precise standards. Your eye may be able to discern differences in shine and brilliance, but you may not be able to discern the subtleties of proportioning. The percentages on the report should fall within a fairly accurate range for the stone to be judged as acceptable, excellent, or poor.
Some reports also give information about the crown angle. The crown angle tells you the angle at which the crown section was cut. This angle affects the depth and table percentage. Usually when the crown angle is between 34 and 36 degrees, the table and depth are excellent; between 32 and 34, good; between 30 and 32 degrees, fair; and less than 30 degrees, bad. If the exact crown angle is given, it is likely to be considered acceptable. If not, there is a statement indicating that the vertex angle exceeds 36 degrees or is less than 30 degrees.
Depth Percentage
A round diamond cut with a depth percentage between 58 and 64 percent is usually a beautiful, vibrant stone. However, you should note that belt thickness affects depth percentage. A high depth percentage can result from a thick or very thick girdle. So when you check the depth percentage on the diamond report, also check the girdle information.
Stones with a depth percentage greater than 64% or less than 57% are usually too deep or too shallow to show maximum beauty and should sell for less. If the depth percentage is too high, the stone will look smaller than its weight suggests. If the depth percentage is exceptionally high, brilliance can be severely compromised. Diamonds that are so flat, i.e. stones with such little depth, that they have no brilliance and liveliness at all. When dirty, such stones look no better than a piece of glass.
We avoid diamonds with a depth percentage greater than 64% or less than 57%. If you are attracted to such diamonds, remember that they should sell for a lot less per carat.
Table Percentage
Round diamonds cut to tables of 53% to 64% typically produce beautiful, vibrant stones. Diamonds with smaller tables usually show more fire than those with larger tables, but stones with larger tables can have more brilliance. As you can see, the width of the table affects the personality of the diamond, but deciding which personality is more desirable is a matter of personal taste.
Finished
Under Finish on the Diamond Report is an evaluation of the diamond’s polish and symmetry. Polish serves as an indicator of the cutter’s diligence. The quality of the stone’s polish is a factor that cannot be disregarded when evaluating a diamond’s overall quality, as well as its cost and value. Polish can be described as excellent, very good, good, fair or poor in the report. The price per carat should be lower for “fair” or “poor” polished diamonds. The cost per carat is usually higher for “very good” or “excellent” polished diamonds.
Symmetry describes several factors:
How the facet edges are aligned with each other;
whether or not facets from one side of the diamond match corresponding facets on the opposite side; whether or not the facets in the upper section of the diamond are properly aligned with the corresponding ones in the lower section.
If the symmetry is described as “fair” or worse, something is wrong.
When evaluating symmetry, the most important area to check is the alignment of the crown (top) to pavilion (bottom). If it’s not good, it makes a visual difference in the beauty of the stone and, accordingly, in its price. To check for proper alignment here, simply look at the diamond from the side to see if the facets just above the girdle are aligned with the facets just below the girdle or not.
If the top and bottom facets are not aligned, this indicates a sloppy cut and, more importantly, the diamond’s overall beauty is compromised. This reduces the price more than other symmetry errors.
How does the belt affect the value?
The belt is another important element detailed in diamond grading reports. The report indicates whether the belt is polished or faceted and how thick it is. Belt thickness is very important for two reasons:
It affects the value and
it affects the durability of the diamond. Belt thickness ranges from extremely thin to extremely thick. Diamonds with excessively thin or thick belts usually sell for less than other diamonds. An extremely thin belt increases the risk of chipping. Keep in mind that despite their legendary hardness, diamonds are brittle, so very thin edges pose a greater risk.
If a diamond has an extremely thick girdle, its cost should also be reduced somewhat because the stone will appear smaller than another diamond of the same weight with a more normal girdle. This is because the thickness of the belt itself consumes additional weight.
There are some cases where a very thick belt is acceptable. Shapes with one or more points, such as pear, heart, or marquise, can have thick to very thick belts at the points and still be within the acceptable range. Here, the extra thickness in the belt helps protect the tips themselves from chipping.
In general, a diamond with an extremely thin girdle should sell for less than one with an extremely thick girdle because of the diamond’s increased susceptibility to chipping. However, if the girdle is much too thick (as with older diamonds), the price can also be significantly lower, since the stone nubs appear significantly smaller than other diamonds of comparable weight.
The culette
The culet looks like a dot at the bottom of the diamond, but usually it’s another facet, a tiny, flat, polished surface. This facet should be small or very small. A small or very small culet is not noticeable from above. Some diamonds today are sharp. This means that there really is no culet, but instead the stone has been cut straight to a point. The larger the culet, the more visible it is from above. The more visible, the lower the cost of the diamond. Diamonds described with large or “open” culets, such as old European or old mine cut diamonds, are less desirable because the appearance of the culet causes a reduction in sparkle or brilliance at the center of the stone. These stones usually need to be re-sharpened and their price should reflect the need for re-sharpening. For the same reasons, a chipped or broken Topas culet will seriously detract from the beauty of the stone and greatly reduce the cost.
