Clarity is considered one of the most important of the 4 C’s when looking for a diamond. Clarity is often enhanced, which is something you may not know even after you have purchased the diamond of your dreams.
There is a technique called fracture filling that has recently become popular, even though it originally was started in 1982 by Mr. Zvi Yehuda of Israel. It is a process that melts a crystal-like substance into the cracks and fractures of a diamond that is unlikely to be of any value.
It can also be filled with a type of molten glass made special by Yehuda, but no one can tell for sure, as the techniques are relatively unknown. We do know that it uses varying degrees of heat and slowly fills in every crack on the surface possibly using a vacuum method to keep the stone from breaking completely from the heat. The stone is then cooled down and polished to remove any excess filling.
To an untrained eye, it is completely unnoticeable and often is only found under a microscope.
There are some subtle ways in which you can tell if you have a clarity enhanced diamond, such as the flash effect, cloudy surfaces, gas bubbles in the diamond, as well as a cracked texture.
To make sure that your diamond is not fracture filled, you should ask for a written statement from your jeweler regarding any clarity enhancement techniques it may have used and any lab certificates it has.