Changing the Nature of Diamonds
Artificial treatments can improve a diamond’s color or clarity . If a diamond is priced based on its appearance after treatment, its price will be misleading.
Buyers have the right to know exactly whether a gemstone is a natural diamond, a diamond simulant or a laboratory-grown diamond, and whether it has been treated to enhance its appearance.
Color optimization
Although many of these diamonds are not commonly found in the market, GIA still tests each one to determine its appearance grade.
Coating comes in two forms. One is to enhance the color of a diamond by using an ultra-thin chemical or plastic coating to mask the undesirable color of the diamond itself. The other is to coat a diamond simulant with a thin film of lab-grown diamonds to give it some of the properties of natural diamonds.
HPHT is an abbreviation for high-pressure, high-temperature. HPHT treatment can effectively change the color of some diamonds to colorless, pink, blue, green, yellow-green or yellow. This treatment can only be identified in a well-equipped laboratory.
The photo above shows a 6.61 ct diamond before and after HPHT annealing to remove color. On the left is the diamond before annealing, which is considered a Fancy yellow-brown. On the right is the diamond after annealing, which is graded “L” (light yellow).
Clarity Optimization
There are two main treatments used to improve diamond clarity: laser drilling and fracture filling.
Laser drilling is often used to remove tiny dark inclusions from diamonds. The laser drills a small hole into the diamond to enter and burn away the inclusion, or to create a channel to inject a bleaching agent to improve the appearance of the inclusion.
Shown at 63x magnification, this 3.28 ct round brilliant cut diamond has been laser drilled to remove inclusions.
Fracture filling is used to hide white cracks inside diamonds, called “feathers”. The method is to inject glass-like fillers into the cracks of the diamond, making the cracks less obvious, thereby improving the apparent clarity of the diamond. Since the fillers may be damaged or removed during the routine cleaning and repair of diamonds, there is still controversy in the industry about the use of this technology. Successful fracture filling is very hidden, so it takes a professional diamond appraiser to identify it.
How Does a GIA Diamond Grading Report Help You Identify Treated Diamonds?
GIA will not issue grading reports for any diamond that has undergone non-permanent or unstable treatments, such as coatings or fracture fillings.
However, GIA will issue a report for diamonds that have been laser drilled or HPHT treated, and will note the treatment on the report. As a precaution, GIA will also laser inscribe the diamond’s girdle to indicate that the diamond has been color treated.
