Education

The 4 Cs

Because diamonds are so valuable, it’s essential to have a universal grading system for comparing their quality. In the 1940’s and 1950’s, the Gemological Institute of America (GIA) developed four universally accepted characteristics to objectively compare and evaluate diamonds. These characteristics are known as “The 4 C’s” and they consist of Cut, Color, Clarity and Carat Weight. The system allows you to identify the quality of a diamond, compare it with other diamonds, and assess how much a diamond is worth. A diamond’s value can be dramatically affected by modifying any one or more of these characteristics.

Understanding diamond cut starts with the shape of a diamond.  The standard round brilliant is the shape most used in diamond jewelry.  All others are known as fancy shapes, including but not limited to the following: Oval, Cushion, Marquise, Heart, Pear, Emerald, Princess, Radiant and Aascher.

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From a value standpoint, though, cut refers to a diamond’s proportions, symmetry and polish.  The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter.  Without this precision, a diamond wouldn’t be nearly as beautiful. Many gemologists consider cut the most important diamond characteristic because even if a diamond has perfect color and clarity, a diamond with a poor cut will have dulled brilliance.

Cut fuels a diamond’s 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).

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. Many proportion combinations are possible, and these ultimately affect the stone’s interaction with light.

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    Diameter:
    The width of the diamond as measured through the girdle.
  • Table: The flat top and largest facet of a gemstone.
  • Crown: The top portion of a diamond extending from the girdle to the table.
  • Girdle: The narrow band around the widest part of a diamond.
  • Pavilion: The bottom portion of a diamond, extending from the girdle to the table.
  • Cutlet: The facet at the tip of a gemstone. The preferred cutlet is not visible with the unaided eye.
  • Depth: The height of a gemstone measured from the cutlet to the table.
  • Pavilion Depth: The distance from the bottom of the girdle to the cutlet.

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When a diamond is cut too deep, light leaks out of the bottom, brilliance is lost and the center of the diamond will appear to be dark.

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When a diamond is cut too shallow, light leaks out of the bottom, brilliance is lost and the center appears watery, glassy and dark.

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A well-cut diamond will direct more light through the crown.

The color grade of a diamond is a measure of the stone’s colorlessness.  The less color, the higher the value.

Most diamonds found in jewelry stores run from colorless to near colorless, with slight hints of yellow or brown. So called “fancy colored diamonds” come in more intense colors, like pink and blue, but these are not graded on the same scale.

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The color grading system for diamonds uses the letters of the alphabet from D though Z, with “D” being the most colorless and therefore the rarest and most valuable, and “Z” having the most color within the normal range, and being the least valuable, all other factors being equal.  A diamond’s color is determined by looking at it under controlled lighting and comparing them to the GIA’s color scale, which is based on a set of diamonds of known color.

Diamond clarity refers to the absence of unique birthmarks, either internal (inclusions) or external (blemishes), formed deep within the earth under extreme heat and pressure. The less birthmarks, the higher the value.

The GIA Clarity Scale contains 11 grades, ranging from flawless (FL) to diamonds with obvious inclusions (I3), 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 10x magnification.

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  • Flawless (FL): No inclusions or blemishes are visible to a skilled grader using 10x magnification.
  • Internally Flawless (IF): No inclusions and only blemishes are visible to a skilled grader using 10x magnification.
  • Very, Very Slightly Included (VVS1 and VVS2):  Inclusions are difficult for a skilled grader to see under 10x magnification.
  • Very Slightly Included (VS1 and VS2):  Inclusions are minor and range from difficult to somewhat easy for a skilled grader to see under 10x magnification.
  • Slightly Included (SI1 and SI2):  Inclusions are noticeable to a skilled grader under 10x magnification.
  • Included (I1, I2 and I3):  Inclusions are obvious under 10x magnification and may affect transparency and brilliance.

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Diamonds are weighed in metric carats where one carat is equal to 0.2 grams, equal to about the same weight as a paperclip.  Just as a dollar is divided into 100 pennies, a carat is divided into 100 points.  For example, an 80-point diamond weighs 0.80 carats.

It is important to note that (1) carat weight is not the sole measure of a diamond’s size, since cutting a diamond to different proportions can affect its weight and (2) carat weight is not the sole measure of a diamond’s value, since two diamonds of equal weight can have very different values depending on the other members of the Four C’s: cut, color and clarity.

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 example, a 1.02 ct. stone would be described as “one point oh two carats,” or “one oh two.”

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