Gem traders and jewelers did not immediately come to a unified system to evaluate the quality of diamonds.
While it was easy to categorize diamonds by weight and size, color and flaws were often a stumbling block in the negotiations. In addition, each workshop had its own requirements for the equipment used to grade the stones.
Several systems of grading diamonds are now accepted:
- GIA (Gemological Institute of America, United States);
- HRD Antwerp (Belgium);
- CIBJO (Switzerland);
- Scan D. N. (Scandinavian nomenclature).
Let us have a look at the International Diamond Grading System developed by GIA.
Diamonds are usually graded according to the 4C system, introduced by the GIA. The 4C system includes four grading criteria:
- color;
- clarity;
- carat (weight);
- cut.
Clarity and color are the basic characteristics that play a role in determining a diamond’s value.
Clarity and color of lab-grown diamonds
Clarity
The clarity of a diamond is the degree to which inclusions and surface imperfections are visible. Because diamonds are formed deep in the earth’s mantle, extreme temperatures and pressures create unique markings.
Diamonds without any markings are rare, and their rarity has an impact on their price. The International Diamond Rating System defines the clarity of diamonds by the letters FL to I 3. FL is for flawless diamonds, while I 3 is for diamonds with obvious inclusions such as air bubbles or crystalline inclusions.
Every diamond is unique. None of them is absolutely perfect under ten times magnification, although some specimens are close to perfect. Such diamonds are called flawless diamonds. They are so rare that most jewelers have never seen one.
Like the GIA color scale, the clarity grading system was needed because jewelers used to use terms that could easily be misinterpreted. Today, even if you buy a gem from another country, a jeweler will probably use terms like VVS 1 or SI 2, although he may speak French, or Japanese, or English.
Clarity is assessed under 10x magnification or with the naked eye, taking into account size, number, location and color of internal features, as well as, in some cases, surface characteristics.
When judging the clarity of a diamond, attention must also be paid to superficial flaws (pits, scratches) that cannot be removed by polishing without great loss of weight.
All other things being equal, diamonds without internal inclusions are considered to be the most valuable.
The International Diamond Grading System distinguishes between 11 clarity grades, which are defined in the table below. Most stones fall into the VS or SI categories.
| Grade | Explanation | |
|---|---|---|
| FL | Flawless | Flawless, no inclusions or spots are visible when viewed through the 10-times magnification |
| IF | Internally flawless | No inclusions, surface blemishes visible to a qualified appraiser under 10X magnification |
| VVS 1 and VVS 2 | Very, Very Slightly Included | The smallest inclusions, which range from hard to very hard to see, are visible to an experienced appraiser under 10X magnification |
| VS 1 and VS 2 | Very Slightly Included | Very small inclusions, which range from indistinguishable to readily discernible |
| SI 1 and SI 2 | Slightly Included | Slight inclusions that range from plain to very easily discernible with 10× magnification |
| I 1, I 2 and I 3 | Included | Inclusions that are visible at 10-times magnification and can affect transparency and brightness |
Classification by clarity groups
Defects in a diamond are morphological features of the original specimen visible under the 10-times magnification, such as inclusions or defects in the surface, as well as features caused by processing, sorting and transportation, the removal of which leads to a perceptible change in the weight of the diamond.
If there are imperfections that give reflections, the number of imperfections is taken as the number of valid imperfections and their reflections that are visible when viewing the sample from the top of it, perpendicular to the setting.
In this case, stones of 0.30 carat or more with an additional facet, or calette, cannot be classified in group 1. Six-carat diamonds are graded into clarity groups by commission.
Color Rating Scale
The GIA diamond color rating scale is an industry standard. The scale is made up of Latin letters from D to Z, where D is colorless and Z is light yellow or brown, that is, the grading goes up as the presence of color increases.
Scale for evaluating the color of lab-grown diamonds
Each letter grade has a well-defined range of color attributes: a group of colorless stones, almost colorless stones, slightly colored stones, very light stones, light colored stones. The classification of diamonds by color is done by comparing them to stones of known color under controlled lighting and clear viewing conditions.
The difference between some colors is so subtle that it is inaccessible to the naked eye. But these small differences greatly affect the quality and price of diamonds.
Many people wonder why the scale does not begin with the letter A. Before the GIA specialists developed the D to Z color grading scale, a number of other systems were little used. They included a system with letters (A, B and C, several A’s for the best stones), numerals – Arabic numerals (0 to 3) and Roman numerals (I, II, III) – as well as descriptive indicators of diamonds, such as “blue gem” or “white-blue.
The use of such grading systems has led to inconsistencies and inaccuracies. Because the creators of the GIA color system wanted a fresh start, they chose the letter D as the initial grade, a letter grade not normally associated with the highest quality.
Fancy diamonds color scale
The GIA grading system for fancy color diamonds is based on the following factors:
- Hue: The GIA uses a color wheel to identify the hue of a fancy color diamond. The color wheel is divided into 12 hue ranges, each of which is represented by a letter. For example, a diamond with a yellow hue would be graded as “Y.”
- Tone: The GIA uses a tone scale to measure the lightness or darkness of a fancy color diamond. The tone scale ranges from Faint (the lightest) to Fancy Deep (the darkest).
- Saturation: The GIA uses a saturation scale to measure the intensity of a fancy color diamond. The saturation scale ranges from Faint (the least saturated) to Fancy Vivid (the most saturated).
- Clarity: The GIA uses the same clarity scale for fancy color diamonds as for colorless diamonds. The clarity scale ranges from IF (internally flawless) to I3 (imperfect).
The GIA grading system for fancy color diamonds is a valuable tool for buyers and sellers of these diamonds. The system provides a standardized way to evaluate the quality of fancy color diamonds, and it helps to ensure that buyers are getting the best possible value for their money.
