Grading Diamonds

Like any collectable, the initial price of a diamond and its ability to increase in value is determined by its rarity. The main factors that influence diamond prices are its color, cut, clarity and carat weight, all being factors of rarity.

Color - The single most important factor in grading and valuing colored diamonds is the color of the stone. The color, hue and tone of the diamond is compared to the lightness or darkness of the color to determine the grading, or quality of the stone (see table). The body color of a stone greatly affects the appearance of a diamond and its price. Color is part of the natural composition of the diamond and never changes over time. It is caused by varying quantities of nitrogen and other trace elements present in all diamonds, displacing the carbon atoms within the crystal's structure.

Faint Very Light Light Fancy Light Fancy Fancy Dark Fancy Intense Fancy Deep Fancy Vivid
GIA Color Grading Scale

Cut - Cut has the strongest influence on the diamonds brilliance. In a well-cut stone, rays of light entering the diamond reflect back to the eye of the observer. In a colored diamond, the unique mixture of color that the viewer experiences is termed “face up color. The cutter of fancy colored diamonds is an artist using the colored diamond rough material to create individual masterpieces with perfectly faceted dimensions and a vibrant color composition. Radiant and brilliant cuts in rectangle, asscher, oval, heart and pear shapes are often used to maximize the color saturation and enhance the viewing of the stone. Ideal proportions, finish and symmetry of a cut are the aim of the cutter, as well as the shape of the stone.

There is a difference between cut and shape. Shape means the outward look of the diamond (such as round, radiant, oval and so on). Cut refers to the reflective qualities of the diamond and is perhaps the most important of the Four C's.

Carat Weight - The origin of the word carat is in the seeds of the carob tree, which were used for the weighing of precious stones in ancient times due to their weight uniformity. A diamond carat is a measurement of its weight not its size, and is not to be confused with Karat, used for determining the purity of gold.

Colored diamonds tend to appear naturally in smaller sizes compared to other diamonds and gemstones. In fact, very few pink diamonds from the Argyle mine in Australia are over one carat in size. At last year's Argyle tender, the largest pink diamond was 2.03 carats and most of the stones were between a third of a carat to one carat in size. Because colored diamonds have a higher price tag and are more readily available in smaller sizes, there is an active sub-carat collector market for these stones.

Clarity - Most diamonds have natural internal characteristics named Inclusions and external features named Blemishes. These occur in the volcanic rock where the diamond is created. Clarity, therefore, refers to the nature, color, number and size of such inclusions or blemishes. Lighter inclusions in fancy colored diamonds are the cause of significant drop in clarity grade.

The majority of colored diamonds contain inclusions because of the chemical structure and pressure required to create one. Colored diamond connoisseurs will acquire a stone based on the color saturation and consider clarity as a secondary issue. The third most expensive stone ever sold was a 0.95 carat red diamond for $926,000 per carat in 1987. This stone was heavily included but because of its rich strawberry color, it sold for a world record price. A comparable D-flawless diamond would sell for $20,000 per carat.

The GIA has established an internationally accepted grading system, according to which Clarity is graded from Flawless to Imperfect as follows:

  • FL (Flawless)
  • IF (Internally Flawless)
  • VVS1 (Very, Very Small inclusions)
  • VVS2
  • VS1 (Very Small inclusions)
  • VS2
  • SI1 (Small/Slight Inclusions)
  • SI2
  • I1 (Imperfect)
  • I2
  • I3

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