Diamond Education

Diamond Education

Diamonds must enjoy a high rating in terms of all 4C's, as universally accepted characteristics that all diamonds are graded by.

  1. The Color
  2. The Clarity
  3. The Cut
  4. The Carat Weight

It is the combination of these four "C's” that determines a diamond's value. By changing any of the characteristics, you can dramatically affect the diamond's value, all other factors being equal.

Understanding Cut
The only quality that is within human control is its cut. A diamond's cut is the result of a craftsman's skill in transforming a rough diamond into a breathtaking gem. A diamond has facets that allow light to enter it, become refracted, and exit in a rainbow of scintillation and brilliance. So it follows that a better cut diamond does a better job of dazzling us with its beauty. Here's the ‘secret' to how a diamond sparkles:

As you can see, the diamond with the correct proportions does a more effective job of refracting light out the top of the stone to your eye. The less-than-ideal cut diamonds allow some light to become lost out the bottom.

There are many factors that go into a well-cut diamond. It must be cut to precise and angles; it cannot be too shallow or too deep; its facets must align properly; its surfaces must be polished to a mirror-like finish. Many of these characteristics are graded on what is known as a diamond grading report, which is created by an independent gemological laboratory and is provided with many diamonds.

An "ideal cut” is a specific set of guidelines that delineate the proportions that give a diamond the highest amount of fire and brilliance. The concept of an ‘ideal cut' diamond originated with a diamond cutter and mathematician named Marcel Tolkowsky, in his dissertation on the subject in 1919. Sometimes called the "Father of the American Brilliant Cut”, Tolkowsky was the first person to show that a diamond with 57 facets that was cut to specific proportions would result in the highest possible fire and brilliance.

Although the proportions of an ideal cut vary depending on which source you talk to (from jeweler to jeweler, country to country), there are certain ranges that are generally accepted as capable of evoking the most desirable fire and brilliance from a stone. These ranges must cause the light entering the diamond to be reflected and dispersed through the table (top), not through the sides or bottom. The ideal cut diamond possesses good symmetry, i.e. its table and girdle are parallel to each other and the culet and table are well centered (see Diamond Proportions diagram below). The facets are also well aligned and symmetrical. Of course, ideal cut diamonds must have excellent polish and high luster.

But most of all, an ideal cut diamond must be cut to bring out the stone's brilliance and fire, not retain the most weight from the rough cut stone. It should not have a crown or pavilion that is too shallow or excessively deep. The girdle should not be too thin, or the stone may chip. If it is too thick, its brilliance may be reduced. If the girdle appears to be a wide band around the diamond, it's probably also too thick. If you can hardly see it, it's probably too thin. A properly cut girdle should be even all the way around.

It's important to note that some independent grading laboratories do not grade a diamond's cut, while others do. The Gemological Institute of America (GIA), for example, does not give an evaluation of the quality of a diamond's cut, only the shape and measurements of the stone. It does, however, give the proportions of the diamond (depth and table percentages, girdle thickness, culet size (if any) as well as a general rating of the stone's finish, including its polish and symmetry. The American Gemological Society (AGS) on the other hand, has its own rating scale for a diamond's cut. This numbering system ranges from 0 to 10:

AGS Cut Grading Scale
2………………..Very Good
3, 4…………….Good
5, 6, 7………….Fair
8, 9, 10………..Poor

A diamond's cut is a complicated evaluation based on many factors, including depth and table percentages, crown angles, girdle thickness and others. Added to that, some independent grading laboratories do not grade cut, making the determination even harder to quantify. We can, however, tell you that an ideal cut diamond generally has a 20 to 30% higher value than one that is just "good”.

Understanding Color
The most important thing to know about color when it comes to diamonds is, the less color a diamond has, the more valuable it is. Diamonds are found in nature in a wide range of colors, from completely colorless (the most desirable trait) to slightly yellow, to brown. So-called ‘fancy color diamonds' come in more intense colors, like yellow and blue, but these are not graded on the same scale.
The color grading system for diamonds uses the letters of the alphabet from D through Z, with ‘D' being colorless and therefore the rarest and most valuable, and ‘Z' being the least. A diamond's color is determined by looking at it under controlled lighting and comparing them to the Gemological Institute of America's color scale, which is based on a set of diamonds of known color, called Master Stones. Here is a diagram showing how a diamond's color is graded:

Diamonds found in nature come in colors ranging from colorless to slightly yellow or brown, to more rare and costly pink, green or blue stones (commonly referred to as 'fancy' diamonds. Excluding 'fancy' diamonds, the ideal color for a diamond is colorless, although this is extremely rare.
A diamond's color is most accurately determined when it is not mounted in a setting, since settings can introduce tints of their own color into the diamond. This is more evident in yellow gold settings, and less so in white gold and platinum settings. Even a trained professional can't always tell the difference between close grades of color in a diamond if it is still mounted in a setting. For this reason, gemological laboratories such as the Gemological Institute of America (GIA) and American Gemological Society (AGS) will only grade diamonds that are unmounted.
Diamonds with a color grade of D, E or F are considered colorless; G, H, I and J are near colorless; K, L and M have a faint yellow tint; N, O, P, Q and R have a very light yellow tint and S, T, U, V, W, X, Y and Z are light yellow. A diamond that is a D color is absolutely colorless, and is therefore the most valuable. However, it's important to understand that color alone does not determine the value of a diamond. All '4Cs' must be taken into account. A diamond of D color that has imperfections or is poorly cut is not as valuable as a stone of a lower color grade that has a superior cut and clarity.

The bottom line:
A diamond's color also has a great impact on its cost. Since 'colorlessness' is the most sought-after trait in terms of color, diamonds that are higher up on the color scale (e.g. D, E, F) will have a greater value. If a diamond with a specific cut, clarity and carat weight is moved to the next color grade, it's possible to see a significant increase or decrease in the per-carat price-all other factors being equal. The idea is to choose a diamond that is as high on the color scale as your budget will allow, taking all 4Cs into account.

Understanding Clarity
Another vital grading characteristic in diamonds is their clarity. This refers to the number, position and size of the inclusions that occur naturally inside diamonds. As you would imagine, the fewer the inclusions, the more valuable the diamond. Here is an illustration that shows the clarity grading scale that has been established by the world's foremost authority on diamonds, the Gemological Institute of America, or GIA:


Flawless; the diamond had no internal or external flaws


Internally Flawless; no flaws inside the stone, minor surface blemishes


Very, Very Small inclusions

VS1, VS2

Very Small inclusions

SI1, SI2

Small Inclusions


Inclusions are easy to locate and may be visible to the naked eye


Inclusions are obvious and are visible to the naked eye


Inclusions are very obvious

You should know that truly flawless or internally flawless (F or IF on the GIA's grading scale) diamonds are extremely rare. It is these inclusions or blemishes that give each diamond its own unique fingerprint, making your particular diamond truly yours. The most important thing to remember when it comes to clarity is that a diamond's inclusions should not be noticeable to the naked eye, nor should they be so excessive that they affect the diamond's durability.

A diamond's ability to refract and reflect light is what makes it so brilliant and so valuable. The way it does this is by allowing light to enter the top of the stone, reflect off the facets that have been cut by a diamond craftsman, and reflect out the top of the stone to your eye. So, the fewer obstacles to this pathway there are, the greater the diamond's clarity will be, which increases the diamond's value (all other characteristics being equal).
Most diamonds contain some blemishes (crystals, clouds, or feathers), which can be found inside the stone (called inclusions). Surface blemishes are not considered a major concern, since they can often be polished away. Crystals are mineral deposits trapped inside the diamond; clouds are small specks or hazy areas that give a milky appearance and feathers are small cracks that are shaped like a bird's feather.
Naturally, inclusions that don't impede the light's passage through the diamond or visibly decrease its beauty will not have a substantial effect on its value. It is more important that any blemishes do not affect the stone's attractiveness or durability, than that the diamond be 'perfect'.
A diamond's clarity is measured using a jeweler's loupe (a small magnifying glass used to view gemstones) under 10-power magnification. The FTC requires all diamond grading be done under 10-power magnification; any inclusions not detected under this magnification are considered to be non-existent.

The bottom line
Since clarity is so critical, it will of course result in differences in value. If a diamond of a particular cut, color and carat weight is moved to the next clarity grade, it's possible to see a significant increase or decrease in the per-carat price - all other factors being equal. The object is to choose a stone with the greatest clarity grade your budget will allow, taking into consideration the other of the 4Cs as well.

Understanding Carat Weight
A diamond's weight is measured in ‘carat', which is a small unit of measurement equal to 200 milligrams. Carat is not a measure of a diamond's size, since cutting a diamond to different proportions can affect its weight. (The word ‘Karat' is used to express the purity of gold, and is not used in relation to diamonds.) Here is a diagram that shows the relative size of various carat weights in a diamond that is cut to the same proportions.
Note: the diamonds illustrated are not shown actual size.
Carat Weight Scale

The word carat actually comes from the word carob (as in carob seeds), which is how ancient cultures measured the weight of diamonds on their scales. In 1913, however, the weight was standardized internationally and adapted to the metric system.
Although they can be measured when mounted in jewelry, diamonds are most accurately weighed when they are not mounted in a setting. In fact, gemological laboratories such as the Gemological Institute of America (GIA) and American Gemological Society (AGS) will only grade diamonds that are unmounted. A diamond grading report will tell you the exact carat weight, to the nearest hundredth of a carat, for that particular diamond. Each Carat is divided into 100 parts called 'points.' So a 1-carat diamond has 100 points, a ¾ carat has 75 points, etc. Points in a fraction of one carat are measured within ranges, so that a ¾ carat diamond may have between .69 and .82 points and still be considered a ¾ carat. Here's a table of size and weight ranges:

Carat Fractions and Their Decimal Equivalents:


Decimal Equivalent



.09 - .11



.12 - .13



.14 - .15



.16 - .17



.18 - .22



.23 - .28



.29 - .36



.37 - .44



.45 - .58



.59 - .68



.69 - .82



.83 - .94



.95 - 1.05

Remember, all diamonds are not created equal. Two diamonds of equal Carat Weight may vary substantially in price due to their Cut, Color and Clarity. Also, a diamond's weight can be 'hidden' in different parts of the stone. For example, you can have a well-cut diamond, whose weight is distributed properly, a diamond that is cut too shallow to make it wider and heavier, but not the most brilliant, or one that is cut too deeply, to add weight to the bottom of the stone - again compromising its ability to radiate maximum brilliance.
The bottom line:
The carat weight of a diamond is an extremely important determining factor in its value. Diamonds are valued on a per-carat basis. For example, a diamond of exceptionally high quality may sell for $20,000 per carat, while one of lesser quality may sell for $1,000 per carat. So, a three-carat stone could be $60,000 or $3,000, depending on its per-carat price. Diamond values also increase disproportionately as the size of the stone increases. In other words, a two-carat stone will not necessarily cost twice per carat than a one-carat stone. It could cost much more, since diamonds are rarer in larger sizes. As you take a stone of a particular cut, clarity and color and move its carat weight to the next price category, you may see quite a large increase in the price per carat. Remember that size isn't everything. When choosing a diamond, all 4Cs must be taken into account. The key is to strike a balance among them, while still working within your budget.