Synthetic Diamonds and Detection
Synthetic diamonds are identical to natural diamonds in their chemical and physical properties. Methods to identify these exist and while they can be challenging and sometimes require expensive equipment, they are not thought to be a significant threat. However, very small diamonds that are set into jewelry can be much more difficult to determine their origin.
The word simulant or imitation in gemology is used for any material that looks like the natural gem. Imitations do not have any chemical or physical properties identical to natural diamonds. Therefore, any colorless and transparent gem, whether natural or man-made, can be used as an imitation. Several diamond imitations, most notably cubic zirconia and synthetic moissanite, are known in the market. Neither of these poses great challenges in identification for an experienced jeweler or gemologist.
Diamond Treatments and Detection
It is possible to improve the apparent quality of some lower quality diamond by treating them with one of several methods. Detecting most diamond treatments is a challenge to the entire industry. Some diamonds treatments may be easier to identify. Treatments are done to improve color and/or clarity of diamonds. Here are the main diamond treatments to know about.
- Laser Drilling:
When diamonds have prominent dark inclusions, they may not be very appealing to the eye. Laser drilling for removing these black inclusions developed in the 1960s and had widespread use by the 1970s. The process involves a very fine laser beam opening a microscopic drill hole to reach at the inclusion. This extremely thin tunnel allows an acid bath to enter the diamond and remove the dark inclusion. Although this is done in an effort to improve the appearance of the diamond, one can debate whether it really does since it leaves a drill hole and creates yet another inclusion where there used to be a dark inclusion. Most laser drilling is easy to identify with careful inspection of the diamond through magnification.
- Internal Laser Treatment (a.k.a KM Treatment):
This is a relatively new method of using laser to remove dark inclusions but does not create drill holes or tunnels. Instead, KM Treatment creates a series of fine feathers reaching the dark inclusion from the surface in order to clean them out with acid solutions. The identification is challenging but not impossible when a careful examination is performed via microscope.
Pricing of laser treated diamonds is erratic. Some will lower the price of the diamond due to the drilling process, while others will not, arguing that the diamond may still have the same clarity grade but with slightly improved appearance. GIA and other reputable labs will provide a report for these diamonds since the treatment is permanent. The report and the plot diagram will clearly indicate the treatment. The important thing here is disclosure by the seller. In the U.S., it is required to disclose all diamond treatments. As long as consumers know what has been done, it is then up to them to make an informed buying decision.
- Fracture Filling
Fracture filling is a process involving the use of a lead-based glass that through heating and pressure, is imparted into the diamond, effectively hiding the feathery type of inclusions. The film-like layer of glass is so fine that it does not add significant weight (if any at all) to the diamond. The process is very effective in masking fine breaks in a diamond called feathers. The correct term for this treatment is clarity enhanced, though many in the trade prefer to use the term “fracture-filled.” As long as the treatment is properly disclosed, it again is up to educated consumers to decide if this product is for them. However, since the treatment is not permanent, reputable labs such as GIA will not give a grading report for these diamonds.
Care should be taken with these diamonds. They should not be placed in an ultrasonic cleaner. If repairs are to be done by a jeweler, the jeweler should be informed about the treatment as the high heat generated by a jeweler’s torch would damage the filler. It can be retreated if this should happen.
HPHT is the abbreviation for “High Pressure, High Temperature.” This treatment was perfected in the early 2000s for changing the color of a diamond using nothing more than controlled heating combined with high pressure. The equipment used for this technique is identical to the ones for production of synthetic diamonds. These expensive presses are effective on some diamonds and can change the color from a low yellowish or brownish color all the way up to D, E, or F colorless. The same process can also be used to change some diamonds into fancy color diamonds. Detecting this treatment is the most challenging in the industry. Rarely, microscopic signs are left behind that can be proof positive of the treatment. The best method of detection is advanced spectroscopy that is provided by a lab. Sophisticated equipment can act as screeners for these treatments.
Irradiation of a diamond is used to create fancy color diamonds from off-color inexpensive diamonds. The process is controlled and stable, especially when followed by a controlled heating process called annealing. Today, depending on the type of radiation there are several colors can be created on diamonds. Decades of experimentation and research on irradiation of diamonds resulted in more sophisticated methods and several colors including black. Green, blue, yellow, orange, pink and even red are possible to create through irradiation of diamonds. Detection is a challenge and has almost always required advanced spectroscopy. In some cases, the laboratories may deliver a report indicating the treatment state as undeterminable. While carat sizes or bigger fancy colored diamonds are sent to a lab for detection color origin, most fancy colored melee goes undetected in the market.
There is another way of enhancing the color of a diamond by coating it with a thin layer of colorant. The process, however, is not permanent. This treatment is achieved by applying a thin film to the surface of a diamond partially or completely in order to modify the color. Since coating is a shallow surface modification, due to low durability, it is possible to see shallow damages on the color coating which does not go into the stone. Regardless of their longevity, any ethical practice requires full disclosure.