Diamond Education

The four Cs of diamond grading are Color, Clarity, Carat, and Cut.

A chemically pure and structurally perfect diamond is perfectly transparent with no hue, or color. However, in reality almost no gem-sized natural diamonds are absolutely perfect. The color of a diamond may be affected by chemical impurities and/or structural defects in the crystal lattice. Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value. For example, most white diamonds are discounted in price when more yellow hue is detectable, while intense pink diamonds or blue diamonds (such as the Hope Diamond) can be dramatically more valuable. Of all colored diamonds, red diamonds are the rarest. The Aurora Pyramid of Hope displays a spectacular array of naturally colored diamonds, including red diamonds.

Colors
Diamonds occur in a variety of colors—steel gray, white, blue, yellow, orange, red, green, pink to purple, brown, and black Colored diamonds contain interstitial impurities or structural defects that cause the coloration; pure diamonds are perfectly transparent and colorless. Diamonds are scientifically classed into two main types and several subtypes, according to the nature of impurities present and how these impurities affect light absorption.

History of color grading

Color grading of diamonds was performed as a step of sorting rough diamonds for sale by the London Diamond Syndicate.

As the diamond trade developed, early diamond grades were introduced by various parties in the diamond trade. Without any co-operative development these early grading systems lacked standard nomenclature, and consistency. Some early grading scales were; I, II, III; A, AA, AAA; A, B, C. Numerous terms developed to describe diamonds of particular colors: golconda, river, jagers, cape, blue white, fine white, gem blue, brown, etc.

Grading the normal color range

Refers to a grading scale for diamonds in the normal color range used by internationally recognized laboratories (GIA & IGI for example). 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 ( i.e.  "upside down"— resting on the face one normally looks at). 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 judgement.

Diamonds in the normal color range are graded loose (for example F–G).

Clarity

Diamond clarity is the quality of diamonds that relates to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects, called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut.

Inclusions are solids, liquids, or gases that were trapped in a mineral as it formed. They may be crystals of a foreign material or even another diamond crystal, or may have produced structural imperfections, such as tiny cracks that make a diamond appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone under ten times magnification, which is a magnification standard for loupes used in the gem world.

Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity and are not visible to the naked eyes. However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture.

Diamonds with higher clarity grades are more valued, with the exceedingly rare "Flawless" graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamond technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin.

Gemological Institute of America grading system

History

In 1952, Richard T. Liddicoat, along with Marquis Person, Joe Phillips, Robert Crowningshield and Bert Krashes began to work on a new diamond grading system which they called the "diamond grading and evaluation appraisal". In 1953, they released their new system which assessed three aspects of diamonds; make, color and clarity. They took terminology used in the industry at the time and refined the definitions to produce a clarity scale by which diamonds could be consistently graded. The system at that time contained nine grades: Flawless, VVS₁, VVS₂, VS₁, VS₂, SI₁, SI₂, I₁, and I₂. The 'I' of the I₁, and I₂ grades originally stood for "Imperfect".

During the 1970s, two changes were made to the system. Firstly, the Internally Flawless grade was added, as GIA noticed that many diamonds were being aggressively cut to remove any surface blemishes, and thereby reducing the cutting quality ("make") of the diamonds. The Internally Flawless grade gave diamond manufacturers a choice to leave blemishes on the surface of the stone, and achieve a grade higher than VVS₁. The second change made to the grading system was the introduction of the I₃ grade. This change was made in response to a growing number of diamonds of very low clarity being cut.

The last change to the clarity grading system took place in the 1990s when the term "imperfect" was changed to "included".

Modern GIA grading system

The GIA 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 by 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.

Choice of cut.

The choice of diamond cut is often decided by the original shape of the rough stone, location of internal flaws or inclusions, the preservation of carat weight, and popularity of certain shapes among consumers. The cutter must consider each of these variables before proceeding.

Most gem-quality diamond crystals are octahedra in their rough state (see material properties of diamond). These crystals are usually cut into round brilliants because it is possible to cut two such stones out of one octahedron with minimal loss of weight. If the crystal is malformed or twinned, or if inclusions are present at inopportune locations, the diamond is more likely to receive a fancy cut (a cut other than a round brilliant). This is especially true in the case of macle, which are flattened twin octahedron crystals. Round brilliants have certain requisite proportions that would result in high weight loss, whereas fancy cuts are typically much more flexible in this regard. Sometimes the cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions or to preserve carat weight, since the per-carat price of diamond is much higher when the stone is over one carat (200 mg).

While the round brilliant cut is considered standard for diamond, with its shape and proportions nearly constant, the choice of fancy cut is influenced heavily by fashion. For example, the step cut baguette—which accentuates a diamond's luster, whiteness, and clarity but downplays its fire—was all the rage during the Art Deco period, whereas the mixed Princess cut—which accentuates a diamond's fire and brilliance rather than its luster—is currently gaining popularity. The princess cut is also popular among diamond cutters: of all the cuts, it wastes the least of the original crystal. Older diamonds cut before ca. 1900 were cut in "primitive" versions of the modern round brilliant, such as the rose cut and old mine cut (see History section). Although there is a market for antique stones, many are recut into modern brilliants to increase their marketability. There is also increasing demand for diamonds to be cut in older styles for the purpose of repairing or reproducing antique jewelry.

The size of a diamond may also be a factor. Very small (< 0.02 carats [4 mg]) diamonds—known as melée—are usually given simplified cuts (i.e., with fewer facets). This is because a full-cut brilliant of such small size would appear milky to the human eye, owing to its inability to resolve the stone's dispersive fire. Conversely, very large diamonds are usually given fancy cuts with many extra facets. Conventional round brilliant or fancy cuts do not scale up satisfactorily, so the extra facets are needed to ensure there are no "dead spots". Because large diamonds are less likely to be set in jewelry, their cuts are considered for how well they display the diamonds' properties from a wide range of viewing directions; in the case of more moderate-sized diamonds, the cuts are considered primarily for their face-up appeal.

The dominating round brilliant diamonds are not as trendy as they used to be since the market was overcrowded in the last decades of the century. Simultaneously, giving a fancy diamond cut as a precious jewel on specific celebrations became a part of tradition. A Heart cut diamond has romantic symbolism so it is a common gift for Valentine's Day or wedding anniversary. The pear-shaped diamonds look like a drop of water and the shape is suitable for diamond earrings. The most famous shapes are: Princess, Cushion, Heart, Pear, Marquise, Radiant, Asscher cut, Emerald, Oval.

Size