‘Fracture filled’ or ‘clarity enhanced’ diamonds are those whose fractures or cracks have been filled to restore and enhance their brilliance.
The problem with fractures is that they detract from the beautiful appearance of a diamond, affecting its value and durability. A process for fracture filling diamonds was developed in 1982 by Israeli inventor and diamond cutter Zvi Yehuda, and involves filling surface-reaching cracks in diamonds with molten glass to improve their clarity. It was not until the 1990s that fracture filled diamonds began to appear in the market in considerable quantities.
The glass used has a high refractive index similar to that of diamond, making the fractures less visible. The treatment is understood to be performed under enough heat and pressure sufficient to force the liquid glass into the fractures. The method for fracture filling a diamond tends to improve a diamond’s clarity by one grade and as it is only a thin glass film which is used, the colour or weight of the diamond is not affected.
Only diamonds with small cracks can be fracture filled; the process for fracture will not work successfully for diamonds with large cracks. 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.
What are the advantages of buying a fracture filled diamond?
Yehuda originally said that the ‘advantage’ to fracture filled diamonds is their lower cost and that they create the potential for someone to purchase a larger, cleaner diamond than they would have otherwise been able to afford. However, a person purchasing a fracture filled diamond isn’t actually getting a discount. They will be paying the same price for the grading of the stone before the fracture was filled. The only difference is that a visible inclusion has now been made “invisible” to the naked eye.
What are the disadvantages of buying a fracture filled diamond?
Generally, fracture filled stones are too small or of 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 appearance may worsen over time. It can therefore be difficult to know exactly what you are buying or if the price is right.
The GIA Gem Trade Laboratory (GTL) conducted an extensive study of fracture filled diamonds, published in the 1994 (Autumn) issue of Gems & Gemology Magazine. The GIA scientists determined firstly that “prolonged exposure – or numerous short exposures – to commonly employed cleaning methods may sometimes damage filling substances.” Secondly, it was concluded that “re-polishing of jewellery 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.”
A diamond treated with the Yehuda clarity enhancement process is purported to last under every day wear and tear as well as an untreated diamond. However, fracture fillings can fall out or become damaged. A jeweller working on a piece of jewellery that contains a fracture filled diamond should exercise care while setting or re-tipping the prongs that hold the diamond because the enhancement process can be damaged by temperatures in excess of fourteen hundred degrees or mild acids. Even still, many jewellers will not handle a fracture filled diamond because of the risks.
Also, new types of fillers have been developed which are reported as being more durable and less likely to alter colour over time or leak out during a jewellery repair process.
The US Federal Trade Commission (FTC) Guides and The World Jewellery Confederation (CIBJO) regulations state that all fracture filled stones are required to be disclosed as such at point of sale. This is positive, as it is always an advantage to know exactly what one is purchasing. Still, it is not unheard of for jewellers to unknowingly sell fracture filled diamonds. If you should discover that you were unknowingly sold a fracture filled diamond, contact your jeweller immediately and they should offer you a free replacement pending proof of your discovery from an appraiser. If they do not, you are entitled to take legal action.
To try and spot a fracture-filled diamond yourself, you can easily detect them by shaking the stone from side to side under a microscope; you will notice a ‘flash effect’, a play of bright colour spanning from an electric purple to an orange or yellow. If a diamond has been tampered with a lot the colour of the glass itself can also be a giveaway; often a yellow-brownish shade visible in transmitted light, it can even impact the overall colour of the diamond.