The Essential 7C's
Clarity Enhancement/Fracture Filled Diamonds
'Fracture filled' or 'clarity enhanced' diamonds are those
whose fractures or cracks have been filled in to restore and enhance
their brilliance. The process for fracture filling diamonds was
developed in 1982 by Israeli diamond cutter Zvi Yehuda and involves
filling surface-reaching cracks with molten glass to improve the
diamond’s clarity. Yet, it was not until the 1990s that fracture filled
diamonds began to appear in the market in abundance.
The glass used has a high refractive index similar to that of
diamond, making the fractures less visible. The treatment is performed
under heat and pressure, sufficient to force the liquid glass into the
fractures. This method tends to improve a diamond’s clarity by one grade
but it doesn’t affect the colour or weight of the gem. Only diamonds
with small cracks can be fracture filled. However, it is important to
note that many diamonds contain minute internal "cracks", sometimes
described as “feathers” by the retailer, that do not pose a threat to
the integrity or life span of the diamond.
The process of fracture filling divides opinion among
jewelers, with many attesting to their advantages and disadvantages.
Yehuda originally said that the advantage to fracture filled diamonds is
their lower cost, creating the potential for someone to purchase a
larger, cleaner diamond than they otherwise would have been able to
afford. However, purchasing a fracture filled diamond doesn’t guarantee a
discount as they will be paying the same price for the grading of the
stone before the fracture was filled. The only difference being that a
visible inclusion has now been made "invisible" to the naked eye.
Furthermore, fracture filled stones are often too small or too low
quality and are therefore rarely submitted to gemological laboratories.
Laboratories will not provide a clarity grade as the enhancement is not a
permanent treatment and the stone’s appearance can diminish over time.
Subsequently, it is difficult for the buyer to know exactly what they
are buying or if the price is right.
Fortunately it is easy to spot a fracture-filled diamond;
simply shake the stone from side to side under a microscope and you will
notice a ‘flash effect’, a play of bright colour spanning from a purple
to an orangey-yellow. If a diamond has been tampered with the colour of
the glass can also be a giveaway as a yellow-brownish shade is often
made visible in transmitted light, even impacting upon the overall
colour of the stone.