Many diamond flaws must be magnified to be seen.

Diamond quality and value is judged by the four c's of carat, cut, color, and clarity. Clarity, which can range from the highly prized "flawless" all the way down to the far less impressive "I-3" is a determination of the number of flaws that are found inside the diamond. These flaws, not all of which are visible to the naked eye, can take a number of forms.

Philip Press began his jewelry career at the age of 15 as an apprentice to a master European craftsman and platinumsmith. Now 37, Press is Chief Designer of Los Angeles' Renaissance Platinum, a preferred retailer of discerning jewelry aficionados and celebrities. Here he offers a guide to the most common diamond flaws:

• Inclusions:
  The majority of diamond flaws are known as inclusions, which are bits of foreign matter suspended within the diamond. Sometimes these can be readily seen, but often they are only visible only through magnification.

• Crystals:
  The most popular type of an inclusion is another crystal that's actually growing inside of a diamond. For example, you can have diamonds growing inside of diamonds and rubies growing inside of diamonds.

• Carbon:
  Diamonds are made entirely of carbon and start out as carbon's more common form, graphite. If the diamond does not fully crystallize when being born, it can contain typical inclusions, which are tiny specks of black carbon.

• Cracks:
  Other types of flaws to look out for include pressure cracks, cleavages and other types of fractures. These may form when a diamond is being born, or may result from the cutting and polishing process.

• Check for certification:
  The most desirable diamonds are the ones that are void of any inclusions or flaws, with value dropping as the clarity rating drops. The best way to ensure that you are buying a diamond of a particular clarity is to make sure that it is certified by a credible gemological laboratory.

For more information about diamonds, check out the following organizations or websites:

Renaissance Platinum
www.platinumrings.com/

American Museum of Natural History: The Nature of Diamonds
www.amnh.org/exhibitions/diamonds/

Diamonds.net
www.diamonds.net

Diamond Review.com
www.diamondreview.com/

Diamond Cutters International: Diamond Education
www.diamondcuttersintl.com

Diamond Engagement Rings Guide
www.thediamondbuyingguide.com

Next: Buying an Engagement Diamond