GIA’s D-to-Z color-grading scale, Flawless-to-I3 clarity-grading scale, and Excellent-to-Poor cut-grading scale are all recognized by gem and jewelry professionals everywhere. And, by extension, the GIA Diamond Grading Report, Diamond Dossier®, and Gemological Identification Report are considered to be the world’s premier evaluations of gem quality and authenticity.
How did the 4Cs of Diamond Quality Come to Be?
Because diamonds are so valuable, it’s essential for industry professionals to have a universal grading system when comparing diamond quality. In the mid-twentieth century, GIA developed the International Diamond Grading System™ and the 4Cs as a way to objectively compare and evaluate diamonds. The Four Cs of diamond quality will give you a multitude of information about a diamond’s characteristics and value, but they can’t begin to describe one elusive quality – beauty. To do that, you’ll need to experience the diamond with your own eyes.
CARAT WEIGHT
Because even a fraction of a carat can represent a considerable difference in cost when purchasing diamonds, exact precision is crucial. In the diamond industry, weight is measured to a thousandth of a carat and rounded to the nearest hundredth. Each hundredth is called a point (a 0.25 ct. diamond would be called a “twenty-five pointer”). 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.”)
The COLOR
GIA’s diamond color-grading scale is the industry’s most widely accepted grading system. The scale begins with the letter D, representing colorless, and continues, with increasing presence of color, to the letter Z. 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 that they are invisible to the untrained eye. But these slight color differences make a very big difference in diamond quality and price.
Colored Diamonds, Gemstones and Pearls
While most diamonds are in the colorless to light yellow range, some have a natural color that is deep, distinct, and opulent. These are known as fancy-color diamonds and are often blue, brown, or pink. Unlike colorless and near-colorless diamonds which are valued for their lack of color, fancies are valued for the intensity of their color. Colored diamonds are a small but increasingly popular segment of the diamond market. The physical conditions necessary to color a diamond naturally occur very seldom, making natural color diamonds extremely rare. For every natural color diamond, there are 10,000 colorless ones that have made the trip from the earth’s depths to its surface. It is this entirely natural process of geographical formation which ensures that each natural color diamond is one of a kind.
The formation of natural color diamonds is a process that requires the presence of additional trace elements and distortions to the typical diamond crystal. During the creation of a diamond, if an element interacts with its carbon atoms, the color can change. Natural radiation and pressure on a diamond’s structure can also intensify its color.
Rather than emphasizing the brilliance and fire coveted in near-colorless diamonds, these stones are all about the color intensity. The Argyle mine in Western Australia launched a massive marketing campaign some time ago that helped change the public’s perception of these previously overlooked diamonds. The 1987 sale of the Hancock Red, at a record auction price of $926,000 per carat, further magnified the allure of fancies.
Color Grading of Fancy Diamonds
GIA’s system for color-grading colored diamonds was developed in the mid-1950s and revamped in the mid-1990s. The diamond color grading system expresses color using the attributes of hue (the characteristic color), tone (the color’s relative lightness or darkness), and saturation (the strength or weakness of the color). Using controlled viewing conditions and color comparators, the grader determines the stone’s color from one of 27 hues. The fancy grade describes the stone’s tone and saturation with romantic names like “Fancy Light,” “Fancy Intense,” and “Fancy Vivid.”Today, the GIA color grading system for colored diamonds is used worldwide. Many of the most famous colored diamonds, including the Blue Hope, the Dresden Green, and the Hancock Red, have been examined by the GIA laboratory using GIA’s color grading system.
GIA offers two types of diamond grading reports for colored diamonds. The GIA Colored Diamond Grading Report contains the same comprehensive diamond information as the GIA Diamond Grading Report. In addition, the GIA Colored Diamond Identification and Origin Report, known as the color-only report, gives a color grade and the nature of the color.
Colored Gemstones
While renowned for its diamond grading expertise, the GIA Laboratory also receives a vast array of colored gemstones for identification—and its work in this area has been equally remarkable. Over the decades, the Institute has created a database of information on more than 100,000 individual gemstones. Using this database and sophisticated analytical tools, GIA researchers can pinpoint a gem’s identity, and depending on the gemstone, even it's geographic orgin. They also distinguish synthetics, simulants, and stones that have undergone treatment. A particularly important activity involves determining the origin of color in gemstones—whether it is natural or the result of a treatment process. The GIA Laboratory applies the same item identification and tracking procedures to colored stone identification as it does to diamond grading.
Pearl Identification
Over the past 100 years, discoveries in pearl culturing have revolutionized the industry, all but completely replacing natural pearls with cultured pearls. By the end of the 20th century, several types of cultured pearls were being produced in an overwhelming variety of colors, shapes, and sizes.In response, GIA sought to create a standard for pearl grading and terminology—much as it had with diamonds in the 1950s. Its pearl-grading system, launched in 1998, was based on GIA's 7 Pearl Value Factors™: size, shape, color, luster, surface quality, nacre quality, and matching.
Diamond Clarity refers to the absence of internal inclusions or external blemishes.
Because they are created deep within the earth, most diamonds contain unique birthmarks called inclusions (internal) and blemishes (external). Diamonds with very few birthmarks are rare and, of course, rarity affects a diamond’s value. Using the International Diamond Grading System™, created by GIA, diamonds are given a clarity grade that ranges from flawless (FL) to diamonds with more prominent inclusions (I3).Every diamond is unique. But none are absolutely perfect even though some come close, even under 10× magnification. Known as flawless diamonds, they are exceptionally rare. Most jewelers have never even see one.
The GIA Clarity Scale contains 11 grades, with most readily available diamonds falling into the VS or SI categories. In determining a clarity grade, GIA considers the size, nature, position, color or relief, and quantity of clarity characteristics visible under 10x magnification.
- Flawless (FL)
No inclusions or blemishes are visible to a skilled grader using 10× magnification - Internally Flawless (IF)
No inclusions and only minor 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 - Imperfect (I1, I2, and I3)
Inclusions are obvious under 10× magnification and may affect transparency and brilliance
CUT fuels the diamond’s fire, sparkle, and brilliance.
Though extremely difficult to analyze, the cut of a diamond has three attributes: brightness (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the light flashes – or sparkle – when a diamond moves).
An understanding of diamond cut begins with the shape of a diamond, with the standard round brilliant dominating the majority of diamond jewelry. All other diamond shapes are known as fancy shapes or fancy cuts and include the marquise, pear, oval, and emerald cuts. Hearts, cushions, triangles, and a variety of other new shapes are also gaining popularity in many forms of 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, the girdle, and the pavilion. A round brilliant cut diamond can have either 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion, 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 synchronicity 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. See more : http://gia4cs.gia.edu/
