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Diamonds - the 4 Cs

  Carat Weight
  Cut (the most important)

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Gems from the Lab


Diamonds - The 4 Cs


The finest and most expensive diamonds are totally without color, like a drop of distilled water. The rainbow hues a diamond flashes derive from the light it separates into the colors of a spectrum. Diamonds of lesser quality have a yellowish or brownish cast.

Judging color is a job that can be performed only by experts with proper gem lab equipment. To grade color, the gemologist places the diamond under white light that is constant and free of ultraviolet rays. The stone is placed table down (that is, top down) and viewed through the pavilion. It is more difficult to judge color if the stone is already mounted.

The tested diamond is compared to a set of five master stones whose colors have been accurately graded and certified by the Gemological Institute of America.

Master Set of Grading Stones

The GIA color grading scale ranges from D through Z. (A, B and C are not used to avoid confusion with other grading systems that use only those three letters.)

The gemologist assigns the stones a specific letter grade. All other things being equal, the lower the color grade, the lower the stone's value.

"Fancy Colored" Diamonds

Diamonds are found in almost every color. The Hope diamond is blue. Other diamonds are canary yellow, pink, rose, and green.

To avoid confusion, diamonds of intense color are referred to as "fancies."

Diamonds of intense color are rare in nature. Those of exceptional quality are very expensive and considered collector's items.

The majority of "fancy colored" diamonds are not natural in color but are color enhanced by irradiation or other means. These treatments are done to diamonds of poor color that would have low value in their natural state.

Shopping Considerations and Caveats

Buyer's Tip

Purchase quality diamonds only from a jeweler who uses a GIA-certified set of master color-grading diamonds. Ask whether the seller has such a set. Cubic zirconium (imitation diamond) stones are not acceptable. Reliable gemologists know that only diamond can be used for grading diamond.

Buyer's Tip

Diamonds that have been irradiated to intense colors can offer some really attractive prices, compared with colorless diamonds or naturally-occurring fancies. The irradiation treatment for color is both safe and permanent.

The other 3 Cs...

Carat Weight 
Cut proportions