Clarity Enhanced/Fracture Filled Diamonds: While the words "clarity enhanced" might lead you to believe that a diamond has been highly-polished to enhance its brilliance, it's a sucker term.  "Fracture Filled" is a better wake-up call for naive wannabe diamond buyers, and anytime you see a great deal on diamond, it's either stolen or "treated," "clarity enhanced" or "fracture-filled."  Legally, this must be disclosed in writing as "clarity enhanced" or "fracture filled."

The "clarity enhancement" process was developed in 1982...by Israeli inventor and diamond cutter Zvi Yehuda. It involves filling cracks in diamonds with molten glass to improve their clarity.  These treated diamonds did not begin to appear in the market in substantial quantities until the 1990's. By filling the cracks and fractures of diamonds with a clear, colorless substance, the repaired diamond has a "startling" degree of clarity enhancement. 

How does it work? Using a secret ingredient that's introduced at extremely high pressure (50 atmospheres) and temperature (400°C), Mr. Yehuda's process is able to hide cracks in a diamond. His method is far more difficult to discern. Most dealers using only a loupe may not be able to identify the treated stones.  Only diamonds with small cracks can be treated, the process will not work for diamonds with large cracks.  The enhancement process tends to improve a diamonds clarity by one grade and does not affect the color or weight of the diamond because only a thin glass film is used.  According to Yehuda, the "advantage" to these treated diamonds is cost and that they create the potential for a person to purchase a larger, cleaner diamond than they would have otherwise been able to afford.

It's all semantics...know what they mean before you nod your head and hand over a credit card: Many diamonds contain minute internal "cracks" that don't pose a threat to the integrity or life span of the diamond, but many retailers frequently refer to cracks as "feathers" because the term is less disturbing to their customers

What are the disadvantages of buying a fracture filled diamond?  The GIA Gem Trade Laboratory (GTL) conducted an extensive study of fracture filled diamonds and published their results in the Fall 1994 issue of Gems & Gemology Magazine.  The GIA scientists concluded that "prolonged exposure - or numerous short exposures - to commonly employed cleaning methods may sometimes damage filling substances."  Dover's Translation?  That big diamond you got for next to nothing may eventually split.  Nice, huh?

It's also been determined that "repolishing of jewelry and repair procedures involving direct exposure to heat (such as re-tipping of prongs) may damage and partially remove the filler from such treated diamonds.