The Four C's
Gemologists and jewelers assess the physical attributes of diamonds using the 4Cs classification system – cut, carat, color and clarity.
The 4Cs classification enables the comparison and valuation of diamonds. No one 'C' is more significant than another, and none will diminish in value over time.
A diamond's beauty is based on far more than these characteristics. Each one was formed billions of years ago and has travelled a long and arduous journey from deep within the Earth.
And while most of a diamonds' qualities are defined by nature, it takes a master craftsman to unlock the diamond's true brilliance, fire and beauty.
Carat
Diamonds and other gemstones are weighed in metric carats: one carat is equal to 0.2 grams, about the same weight as a paperclip. (Don't confuse carat with karat, as in "18K gold," which refers to gold purity.)
Just as a dollar is divided into 100 pennies, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats. But two diamonds of equal weight can have very different values depending on the other members of the Four C's: clarity, color and cut. The majority of diamonds used in fine jewelry weigh one carat or less.
Because even a fraction of a carat can make a considerable difference in cost, precision is crucial. In the diamond industry, weight is often measured to the hundred thousandths of a carat, and rounded to a hundredth of a carat. Diamond weights greater than one carat are expressed in carats and decimals. (For instance, a 1.08 ct. stone would be described as "one point oh eight carats," or "one oh eight.")
How did the carat system start?
The carat, the standard unit of weight for diamonds and other gemstones, takes its name from the carob seed. Because these small seeds had a fairly uniform weight, early gem traders used them as counterweights in their balance scales. The modern metric carat, equal to 0.2 grams, was adopted by the United States in 1913 and other countries soon after. Today, a carat weighs exactly the same in every corner of the world.
Often mistaken with size, carat it is actually a measure of weight.
The term carat is a derivative of the word carob. Carob seeds, which are surprisingly uniform in weight, were used as a reference for diamond weight in ancient civilizations. One carob seed equaled one carat.
One carat is equivalent to 200 milligrams. One carat can also be divided into 100 'points'. A .75 carat diamond is the same as a 75-point or 3/4 carat diamond.
Since larger diamonds are found less frequently in nature, a single 1-carat diamond will cost more than two 1/2-carat diamonds, assuming the color, clarity and cut are the same.
Cut and mounting can make a diamond appear larger or smaller than its actual weight. A diamond's setting should always optimize its beauty.
Color
Diamond color is all about what you can't see. Diamonds are valued by how closely they approach colorlessness – the less color, the higher their value. (The exception to this is fancy-color diamonds, such as pinks and blues, which lie outside this color range.)
Most diamonds found in jewelry stores run from colorless to near-colorless, with slight hints of yellow or brown.
GIA's color-grading scale for diamonds is the industry standard. The scale begins with the letter D, representing colorless, and continues with increasing presence of color to the letter Z, or near-colorless. Each letter grade has a clearly defined range of color appearance. Diamonds are color-graded by comparing them to stones of known color under controlled lighting and precise viewing conditions.
Many of these color distinctions are so subtle as to be invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.
Why does the GIA color grading system start at D?
Before GIA developed the D-Z Color Grading Scale, a variety of other systems were loosely applied. These included letters of the alphabet (A, B and C, with multiple A's for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III) numerals, and descriptions such as "gem blue" or "blue white." The result of all these grading systems was inconsistency and inaccuracy. Because the creators of the GIA Color Scale wanted to start fresh, without any association with earlier systems, they chose to start with the letter D—a letter grade normally not associated with top quality.
Diamonds can be found in many colors, however white-colored or colorless diamonds remain the most popular.
Diamonds are graded on a color scale which ranges from D (colorless) to Z. Warmer colored diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter white colored diamonds (D–J) look stunning set in white gold or platinum.
Color differences are very subtle and it is very difficult to see the difference between an E and an F, for example. Therefore, colors are graded under controlled lighting conditions and are compared to a master set for accuracy.
Truly colorless stones, graded D are treasured for their rarity. Color, however, is subjective. The Incomparable, one of the world's most beautiful diamonds contains hints of brown, smokey amber and champagne colors.
Nature has also created diamonds in shades of blue, green, yellow, orange, and pink. Red is the rarest of all. These diamonds are called 'colored fancies' and are extremely rare and highly treasured.
Clarity
Because diamonds formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, either internal (inclusions) or external (blemishes).
Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond's value. Using the GIA International Diamond Grading System™, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3).
Every diamond is unique. None is absolutely perfect under 10× magnification, though some come close. Known as Flawless diamonds, these are exceptionally rare. Most jewelers have never even seen one.
The GIA Clarity Scale contains 11 grades, with most diamonds falling into the VS (very slightly included) or SI (slightly included) categories. In determining a clarity grade, the GIA system considers the size, nature, position, color or relief, and quantity of clarity characteristics visible under 10× magnification.
- Flawless (FL) - No inclusions or blemishes are visible to a skilled grader using 10× magnification
- Internally Flawless (IF) - No inclusions and only blemishes are visible to a skilled grader using 10× magnification
- Very, Very Slightly Included (VVS1 and VVS2) - Inclusions are difficult for a skilled grader to see under 10× magnification
- Very Slightly Included (VS1 and VS2) - Inclusions are clearly visible under 10× magnification but can be characterized as minor
- Slightly Included (SI1 and SI2) - Inclusions are noticeable to a skilled grader using 10× magnification
- Included (I1, I2, and I3) - Inclusions are obvious under 10× magnification and may affect transparency and brilliance
How did the GIA Clarity Scale come about?
Like the color scale, GIA's clarity grading system developed because jewelers were using terms that were easily misinterpreted, such as "loupe clean," or "piqué." Today, even if you buy a diamond in another part of the world, the jeweler will likely use terms such as VVS1 or SI2, even if her language is French or Japanese instead of English.
Naturally-occurring features called inclusions provide a special fingerprint within the stone. Inclusions are natural identifying characteristics such as minerals or fractures, occurring while the diamond was being formed in the Earth.
The majority of these natural birthmarks are invisible to the naked eye, yet they affect the way light is reflected and refracted within the stone.
Inclusions appear as different shapes, such as crystals, clouds or feathers. These idiosyncrasies often add to the overall character of the diamond.
Containing several birthmarks or inclusions, the Excelsior is considered one on the world's most beautiful diamonds.
Most inclusions are not visible to the naked eye unless magnified.
To view inclusions, gemologists need to use a magnifying loupe that allows them to see a diamond at 10x its actual size.
Inclusions are ranked on a scale of perfection, known as clarity. The clarity scale, ranging from F (Flawless) to Included (I), is based on the visibility of inclusions at a magnification of 10x.
Even with a loupe, the birthmarks in the VVS (Very, Very Slightly Included) to VS (Very Slightly Included) range can be very difficult to find. It is only when a diamond is graded 'I' that it is possible to see the birthmarks with the naked eye.
The position of inclusions can affect the value of a diamond and you should consider the number, size, brightness, nature and position of inclusions.
Some inclusions can be hidden by a mounting, and have little effect on the beauty or brilliance of a stone. An inclusion in the middle or top of a diamond could impact the dispersion of light, sometimes making the diamond less brilliant.
There are very few flawless diamonds found in nature, making these diamonds much more valuable.
Cut
Cut is the factor that fuels a diamond's fire, sparkle and brilliance.
The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter. But without this precision, a diamond wouldn't be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else.
Though extremely difficult to analyze or quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved).
An understanding of diamond cut begins with the shape of a diamond. The standard round brilliant is the shape used in most diamond jewelry. All others are known as fancy shapes. Traditional fancy shapes include the marquise, pear, oval and emerald cuts. Hearts, cushions, triangles and a variety of others are also gaining popularity in diamond jewelry.
As a value factor, though, cut refers to a diamond's proportions, symmetry and polish. For example, look at a side view of the standard round brilliant. The major components, from top to bottom, are the crown, girdle and pavilion. A round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that's known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. A wide range of proportion combinations are possible, and these ultimately affect the stone's interaction with light.
In early 2005, GIA unveiled a diamond cut grading system for standard round brilliants in the D-to-Z color range. This system, the product of more than 15 years of intensive research and testing, assigns an overall diamond cut grade ranging from Excellent to Poor.
How does pavilion depth affect a diamond's cut?
The distance from the bottom of the girdle to the culet is the pavilion depth. A pavilion depth that's too shallow or too deep will allow light to escape through the sides or the bottom of the stone. A well-cut diamond will direct more light through the crown.
Diamond cutting requires great skill and training. The cutter must polish tiny surfaces known as facets onto the rough diamond. This process is what creates the facets known as the crown, culet, table, girdle and pavilion of the diamond.
To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond.
A well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the gem. The facets, when arranged in precise proportions, will maximize the fire life and brilliance of a diamond.
A well-cut diamond will be higher in quality and value than deep or shallow-cut diamonds. Diamonds that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance and a less valuable stone.
Cut also refers to the shape of a diamond – round, square, or pear, for example. Round diamonds are symmetrical and capable of reflecting nearly all the light that enters, so it is the most brilliant of all diamond shapes and follows specific proportional guidelines. Non-round shapes, also known as 'fancy shapes' have guidelines in order that they are considered to be well-cut.
