Diamond Grading Guidelines

Every individual diamond receives a grade based on at least four characteristics.

The Gemological Institute of America has been issuing grading reports on diamonds since 1955. This is trademarked as the International Diamond Grading System. Each diamond report contains grades for carat weight, clarity, color and cut -- known as the "4 Cs" of diamonds.

Carat Weight

Diamonds are weighed using metric carats, with one carat weighing about 0.2 grams. In the same way that a dollar is divided into 100 pennies, a carat is divided into 100 points. A diamond with a score of 50 points for carat weight would therefore weigh 0.50 carats.

Color

Diamonds are considered more valuable the more closely they approach colorlessness. The less color a diamond contains, the greater its value. Most diamonds sold commercially range from colorless to near-colorless, with hints of yellow or brown.

Clarity

In diamond grading, clarity refers to the absence of matter inside it or surface blemishes. Because they are created under great pressure, deep within the Earth, most diamonds contain these unique birthmarks. Diamonds with very few birthmarks are rare and are considered of greater worth.

Cut

The cut of a diamond gives the gem its fire, sparkle and brilliance. Cut has three attributes: brightness, which is the total light reflected from a diamond; fire, the dispersion of light into the colors of the spectrum; and scintillation, which is the way the light flashes when a diamond moves.

References

• Gemological Institute of America: A Guide to Understanding Diamonds
• The Diamond Buying Guide: Four C's of Diamonds

Resources

• GIA: Grading the Four C's of a Diamond