Treatments and Lab-Grown Diamonds

Don’t assume that your diamond has not been treated. Diamonds have been treated for centuries. And every time someone thinks up a new way to color- or clarity-enhance a diamond, gem experts are put to the test to figure out the whys and hows to identify and classify these new gem treatments.

The discovery of diamond treatments remains much the same as ever: Unusual appearing diamonds enter the market, and some observant jeweler asks a gem expert to examine it carefully. Then the discovery of a new treatment for diamond is announced.

Diamonds have been painted, coated, heated, irradiated, and squeezed under high pressure with high temperatures (HPHT) in order to create, enhance, or even eliminate color. Cleavages have been filled with glass-like substances to mask their bright appearance. Lasers have been used to change dark obvious inclusions into white inconspicuous ones.

Curiously enough, once treatments are discovered, the ingenuity of our industry to find ways to detect these treatments and then disseminate that information to the retail jeweler has been relatively quick and successful. New instrumentation is developed and then manufactured for the retail jeweler’s gemological equipment arsenal.

Yet for every diamond treatment that’s detected, another treatment is concocted to mask that treatment’s identifying signature. With greater technological advances, more sophisticated treatments are being developed, which leads to more sophisticated—and often more expensive—identification techniques.

When diamonds are treated to remove the identification criteria, gem experts find themselves examining harder-to-find minute details in order to make that positive identification.

Created Diamonds

Don’t assume your diamond is a natural mined diamond. The first synthesis of diamond was back in the 1950s, and gem-quality synthetic diamond arrived in the 1970s. In the 1980s, new HPHT hydraulic presses helped create commercially available gem-quality fancy yellow lab-grown diamonds. Today, HPHT-grown diamonds may not rival the numbers of natural mined diamonds, but experts estimate that the numbers of cuttable fancy yellow lab-grown HPHT-created diamonds could be in the neighborhood of 75,000 carats this year alone.

The latest breakthrough in the synthesis of diamond, creating colorless and near colorless diamond using carbon vapor deposition (CVD), has the attention of all gem experts. While these lab-grown diamonds are identifiable, cost of identification equipment and the numbers of small lab-grown diamonds entering the market has gem laboratories greatly concerned.

Treated Lab-Grown Diamonds

Who would ever think that you would need to treat a lab-grown diamond? Once you have identified a diamond as being laboratory grown, there’s the question of whether or not the color was also “grown” or has been created by treatment. Using combinations of irradiation, HPHT, and annealing heat, lab grown diamonds can have their color altered.

New Coatings

While coating a diamond is not new, there are new coatings in the marketplace that may be more difficult for the retailer to identify than a simple ink marking along the girdle. Thin film coatings created by physical vapor deposition, such as sputtering and evaporation, are two of the latest techniques being employed to enhance the color of diamonds.

One thing is certain: Identification of treated and lab-grown diamonds is not going to get any easier.

In the meantime, jewelers should be proactive. The charts on the accompanying pages contain the latest information on detecting virtually all known lab-grown diamonds and diamond treatments to help you navigate the maze of the new gemology.

Diamond Enhancement and Synthetic Diamond Detection Chart


What it is:
The use of heat can be a stand-alone process as well as one combined with high pressure, irradiation, or both. The typical use of heat-only treatment is for black diamonds, which also are formed naturally. Heat-only black diamonds commonly start out as industrial-quality drill-bit material. They are then cut and polished into the desired shapes and heated to graphitize the diamond.
How to identify:
Use magnification to see the pitted appearance of the diamond’s surface. You will not get any light through the diamond to see inclusions, unless you are looking at near-surface areas.
HPHT: High Pressure, High Temperature
What it is:
HPHT (always written alphabetically, P before T) is the latest and most difficult to detect of all diamond enhancements. It can change a yellowish, grayish, or brownish diamond into a colorless, near colorless, or fancy color diamond.
How to identify:
Two machines currently are available to detect HPHT: the DiamondSure, which looks for a reaction to very strong short-wave ultraviolet fluorescence, and the infrared spectrometer, which looks for a spectrum line in the infrared.
However, gem laboratories admit that they may not be able to identify 100 percent of all HPHT-treated diamonds.
HPHT-treated diamonds
If your store, like those of most retail jewelers, is equipped only with magnification instruments, look for inclusions that have been graphitized—blackened by the heat. Also look for feathers that have extended due to the pressure. The “second” feather has the appearance of fringe at the internal edge of the original feather.

Laser Drilling

What it is:
Laser drilling is used to reach dark inclusions in a near-colorless stone. The purpose of lasering is to create a means to reach the obvious inclusion with an acid to whiten (“bleach”) it, reducing its contrast. This requires a surface-reaching inclusion, which shows as the telltale laser drill hole.
The advantage of laser drilling is that one can focus on the inclusion that needs to be changed. The diamond is then drilled from the inside out. The most common drilling actually burns the diamond where the laser beam is focused. Once the unwanted inclusion is burnt, the laser’s focus is drawn outward, creating the conduit for the necessary bleaching.
New methods to create more natural-appearing features while lasering include using angular tubes as well as using lasers to create a series of fractures that would eventually make their way to the surface.
How to identify:
To locate laser drill holes/tubes, it’s best to look through the diamond’s pavilion. From this direction one can better see the lengthy tube. However, for drilling that’s closer to the surface, it might also be useful to examine the flat facet diamond surface with overhead illumination in order to find the round drill entry point. The overhead light must be reflecting off the surface in order to help you find the entry point of the laser.


What it is:
Irradiation is used for creating fancy colors, and can only be detected using spectroscopy. Often the color produced by irradiation is an unpopular one, so the diamond is then heated to produce a more pleasant color. This heating, often called annealing, can hide or eliminate the spectrum line or band that one would expect to be able to see using a standard desktop spectroscope.
How to identify:
Sometimes visible light spectroscopes can reveal lines within the spectrum that can prove or strongly indicate irradiation. However, most suspect gems must be examined using UV (ultraviolet) or IR (infrared) spectroscopy.

Clarity Enhancement/Diamond In-Filling

What it is:
Clarity enhancers fill surface-reaching fissures with a high refractive index glass. The high refractive index of the filler helps hide the fissure from view. But the enhancement can melt and discolor under high temperature—for example, during repair. Enhancement companies can repair damaged fillers.
How to identify:
To detect the enhancement, look parallel to or “down” the fissure. A blue/yellow-green or pink/green “flash” will be seen as you rock the diamond back and forth. If you are looking perpendicular to the fissure, you may not see any evidence of the enhancement.

Synthetic Diamonds

What it is:
Currently in the market are Apollo, Chatham, and Gemesis laboratory grown synthetic diamonds. Diamonds also have been created by General Electric, Sumitomo Electric, and De Beers.
Synthetic gem-quality diamonds are created using two different methods. One method involves squeezing elemental carbon atoms together, as in HPHT hydraulic presses. The other allows carbon atoms to precipitate from a chemical cloud, as in CVD (chemical vapor deposition). Both types of synthetic diamonds are detectable using the DiamondSure.
HPHT (High Pressure, High Temperature)
What it is:
HPHT-created diamonds are formed via a method similar to that used to change a stone’s color. Common colors for HPHT-created diamonds are yellow, blue, and pink (after irradiation). Greens and colorless diamonds are possible, but not common.
How to identify:
To identify HPHT-created synthetic diamonds, look for metallic inclusions, which are never seen in natural diamonds. You also may encounter planar clouds, clouds throughout the gem, and hourglass graining. These are the more difficult to identify, since it takes years of experience in examining natural diamonds in order to compare against the synthetic. HPHT diamonds can be magnetic if metallic inclusions are large or plentiful. A small powerful magnet from your local hardware or electronics shop may actually be able to pick the unmounted diamond up off the table.
CVD Synthetics(Chemical Vapor Deposition)
What it is:
Apollo Diamonds is creating synthetic gem-quality diamond using the carbon vapor deposition method. Common colors for CVD diamond are very light browns and near colorless.
How to identify:
CVD diamond inclusions are quite different from those found in HPHT-created diamonds. Because no metallic flux is used to create CVD diamonds, they will not show metallic inclusions or be magnetic. There is similarity in cloud structure, but again, as with HPHT, these can appear natural. Graining is somewhat different, and fluorescence can be as well. Detecting fluorescence using cathode rays is a positive identification method for the laboratories equipped with such a device.