Why It’s Getting Tougher to Detect Treated Diamonds

Advances in technology means treatments are becoming harder to detect, forcing gem labs to play detective to keep up.

Treatments used to enhance the color or clarity of a diamond are not new. In fact, scientists have been toying with techniques since the turn of the 20th century. Over the years, advances in technology and increased demand for lower priced gem materials have contributed to the rise of new treatments.

This has led the industry to a consensus on a variety of treatments for natural diamonds, which are outlined in The Diamond Book by CIBJO, The World Jewellery Confederation. These range from laser drilling and fracture filling to improve the clarity of a diamond, to heating and irradiation or high pressure – high temperature (HPHT) processes for color enhancements.

Techniques for improving diamond clarity are less of an issue today because they are readily identifiable, says GIA lab director Tom Moses. “I’m not so sure there are fewer clarity-enhanced diamonds on the market, they’re just less of an issue when it comes to detection,” he explains. Color enhancements, on the other hand, leave labs playing detective to uncover changing recipes of treatment procedures.

Gem labs and equipment manufacturers are being diligent in their ongoing efforts to detect these treatments to protect consumer confidence and safeguard against those that slip through the cracks undisclosed. More than ever, proper disclosure is imperative for the trade since wrongdoers are constantly developing innovative ways to hide their treatments to enable a higher grading than the diamond deserves.

COCKTAIL OF TREATMENTS

A new and growing trend in diamond enhancements is the use of a “cocktail” of treatments, according to Branko Deljanin, research gemologist at CGL-GRS Swiss Canadian Gemlab. “For 20 to 30 years it was common to use one treatment,” he says. “But in the last decade, treatment facilities are using several techniques that make detection more complex.

There are also post treatments, especially on colorless type IIa diamonds, intended to hide identification features so that less experienced gemologists or appraisers would issue a ‘natural color’ certificate.”

We’re seeing more synthetics on the market that can be irradiated and annealed to produce pink.

Branko Deljanin, research gemologist at CGL-GRS Swiss Canadian Gemlab

Treatments combining HPHT, radiation, annealing, and even surface coating, aiming to alter the color of a diamond, have gained in popularity in the past ten years, says Deljanin. A rainbow of colors is now possible, including more pinks, and rare reds, blues and greens. While most color treatments are stable, there are some that are not — like surface enhancements, which are seen more in pink diamonds to achieve an intense fancy color.

These combinations are also being used in synthetic diamonds, Deljanin says. “We’re seeing more synthetics on the market that can be irradiated and annealed to produce pink,” he explains. “They grow the diamond in one color, with yellow the easiest to grow, and then irradiate and heat the stone to make it pink or red. Treated synthetic pink diamonds can look natural.”

It’s very common that the goal of treatment facilities is to produce natural looking pink diamonds because prices of pink diamonds are higher than other colors, Deljanin notes.

DETECTIVE WORK

The absence of pink graining with higher magnification in larger stones is an indication the color is not natural, but it’s almost impossible to see these features in very small stones, says Deljanin. As a screening technique, he explains you can separate natural pink melee under ultraviolet (UV) light. Natural always fluoresces blue stronger under longwave than shortwave light, while treated fluoresces orange and synthetics red, with the same strong intensity under both longwave and shortwave UV light.

Natural always fluoresces blue stronger under longwave than shortwave light.

Deljanin says most multistep diamond treatments and synthetic diamonds can be identified on the basis of their long and short UV and phosphorescence reactions with reference to some descriptive or pictorial guidelines.