We are here to help you understand how diamond grading works. While some aspects are subjective there are certain things to look out for. Below is information about the 4 C’s (Clarity, Color, Cut, and Carat).
The diamond grading scale is divided into six categories and eleven grades. The clarity categories and grades are:
- Flawless category (FL) diamonds have no inclusions or blemishes visible under 10x magnification.
- Internally Flawless category (IF) diamonds have no inclusions visible under 10x magnification, only small blemishes on the diamond surface.
- Very, Very Slightly Included category (VVS) diamonds have minute inclusions that are difficult for a skilled grader to see under 10x magnification. The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. Pinpoints and needles set the grade at VVS.
- Very Slightly Included category (VS) diamonds have minor inclusions that are difficult to somewhat easy for a trained grader to see when viewed under 10x magnification. The VS category is divided into two grades; VS1 denotes a higher clarity grade than VS2. Typically the inclusions in VS diamonds are invisible without magnification, however infrequently some VS2 inclusions may still be visible. An example would be on a large emerald cut diamond which has a small inclusion under the corner of the table.
- Slightly Included category (SI) diamonds have noticeable inclusions that are easy to very easy for a trained grader to see when viewed under 10x magnification. The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye.
- Included category (I) diamonds have obvious inclusions that are clearly visible to a trained grader under 10x magnification. Included diamonds have inclusions that are usually visible without magnification or have inclusions that threaten the durability of the stone. The I category is divided into three grades; I1 denotes a higher clarity grade than I2, which in turn is higher than I3. Inclusions in I1 diamonds often are seen to the unaided eye. I2 inclusions are easily seen, while I3 diamonds have large and extremely easy to see inclusions that typically impact the brilliance of the diamond, as well as having inclusions that are often likely to threaten the structure of the diamond.
- The European Gemological Laboratory (EGL) introduced the SI3 as a clarity grade. While intended as a range to include borderline SI2 / I1 stones, it is now commonly used to mean I1’s which are “eye clean”, that is, which have inclusions which are not obviously visible to the naked eye.
Grading the normal color range
Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories. The scale ranges from D which is totally colorless to Z which is a pale yellow or brown color. Brown diamonds darker than K color are usually described using their letter grade, and a descriptive phrase, for example M Faint Brown. Diamonds with more depth of color than Z color fall into the fancy color diamond range.
Diamond color is graded by comparing a sample stone to a master stone set of diamonds. Each master stone is known to exhibit the very least amount of body color that a diamond in that color grade may exhibit. A trained diamond grader compares a diamond of unknown grade against the series of master stones, assessing where in the range of color the diamond resides. This process occurs in a lighting box, fitted with daylight equivalent lamps. Accurate color grading can only be performed with diamond unset, as the comparison with master stones is done with diamond placed on its table facet and pavilion side facing upwards. When color grading is done in the mounting, the grade is expressed as an estimated color grade and commonly as a range of color. Grading mounted diamonds involves holding the mounted diamonds table close to the table facet of the master stone and visually comparing the diamond color under the same color conditions as unmounted diamond grading. The resulting grade is typically less accurate, and is therefore expressed as a range of color. While a grading laboratory will possess a complete set of master stones representing every color grade, the independent grader working in a retail environment works with a smaller subset of master stones that covers only the typical grade range of color they expect to encounter while grading. A common subset of master stones would consist of five diamonds in two grade increments, such as an E, G, I, K, and M. The intermediate grades are assessed by the graders judgment.
Diamonds in the normal color range are graded loose, (for example F-G)
Diamond cut is perhaps the most important of the four Cs, so it is important to understand how this quality affects the properties and values of a diamond. A good cut gives a diamond its brilliance, which is that brightness that seems to come from the very heart of a diamond. The angles and finish of any diamond are what determine its ability to handle light, which leads to brilliance.
As shown in the images below, when a diamond is well-cut, light enters through the table and travels to the pavilion where it reflects from one side to the other before reflecting back out of the diamond through the table and to the observer’s eye. This light is the brilliance we mentioned, and it’s this flashing, fiery effect that makes diamonds so mesmerizing.
In a poorly cut diamond, the light that enters through the table reaches the facets and then ‘leaks’ out from the sides or bottom of the diamond rather than reflecting back to the eye. Less light reflected back to the eye means less brilliance.
Wondering what on earth is the diamond’s pavilion? Table? Culet? The graphic and supporting text below explain the various “parts” of a diamond.
- Diameter: The width of the diamond as measured through the girdle.
- Table: This is the large, flat top facet of a diamond.
- Crown: The upper portion of a cut gemstone, above the girdle.
- Girdle: The narrow rim of a diamond that separates the crown from the pavilion. It is the largest diameter to any part of the stone.
- Pavilion: The lower portion of the diamond, below the girdle. It is sometimes referred to as the base.
- Culet: The tiny facet on the pointed bottom of the pavilion, which is the portion of a cut gem below the girdle.
- Depth: The height of a gemstone, from the culet to the table.
CARAT means weight (1 carat = 1/5 of a gram) A diamond weight is a very important factor to its cost. The term “carat ” originated from the seeds of the carob tree. These carob seeds are extremely uniform in eight and this made them the ideal weight unit for the ancient gem traders. This weight (one carob seed) as later standardized to be 1 carat, or 1/5th of a gram, hence a five carat diamond equals 1 gram and 155.51 carats equal one ounce.
The one carat weight is then broken down into 100 equal parts called “points”; 75 points equal 3/4 of a carat, 50 points equal 1/2 of a carat, etc. The significance of the weight is like the other quality grades. Rarity, now by virtue of the diamonds size and weight. Out of 250 tons of diamond ore only a single one carat diamond of gem quality may be found. The value of weight a 100 point (1 full carat) diamond of VS-1 clarity and G body color is generally worth more than an identical VS-1, G color diamond with a weight of .99 carats (less than a full carat). A one point difference in a diamond can make a difference in value.
It is important to understand that the weight of a diamond and its physical size are two different things. Even if the only difference between the two diamonds is .01 carat. Take for example two (2) VS-1, G quality grade 1.00 carat diamonds to show the vast difference in value that the cut will make. One of these diamonds could have the Ideal 6.5 millimeter diameter size one would expect to see in for a 1.00 carat diamond. In the other example, the second 1.00 carat diamond may have only a 5.5 millimeter diameter. Because of this one millimeter diameter size difference, and yet the same carat weight, the smaller diameter diamond would be worth somewhere around 20% less than the Ideal cut diamond of the same weight and quality grade.
These value differences will vary depending upon the size and quality grade of the diamond you may be interested in. This leads us to the fourth quality grade which is the diamonds cut. Every Diamond belongs in a weight grouping class for a range of weight where the prices per carat for each Color and Clarity group combination are listed. The main reason for this is obviously due to rarity in nature, but current market conditions at any specific time plays a very important role. Some sizes and shapes fall in and out of demand due to what is fashionable or considered affordable in society. Because of this, some size groupings for a given shape may have a higher demand and price per carat than one expects, given its rarity in nature.
So to simplify, a diamond in the 1 carat class (1.00-1.49) usually costs more per carat than a diamond less than 1 carat in weight (0.90-0.99). A diamond that is 1 full carat in size, has a higher demand, which causes it to be priced higher. The result is rough stones that could possibly have been cut into beautiful smaller stones are usually cut into not so beautiful 1 full carat stones to get into the higher price range. There are other factors and trade-offs this is just a simplified answer to the reason the cost per carat goes up as the size goes up.