Clarity Enhancement in Gemstones - What Are the Types and Methods

Clarity Enhancement in Gemstones - What Are the Types and Methods

Clarity Enhancement in Gemstones - What Are the Types and Methods

Posted by Sharif Khan on 13th Feb 2016

The State of the Industry: Gem Clarity Enhancement:

Photo Credit: GIA - Gemological Institute of America - An Introduction to Gem Treatments

Once upon a time, all it took was a good gemologist with a magnifying glass to look at a stone and tell you just about everything you needed to know about it. Not so much these days. With advancements in technology, the gem trade has changed significantly, probably irrevocably and forever.

Instead of gemologists, modern detectors of true gem quality have to be educated in the earth sciences, in analytical techniques based on advanced technology--and most importantly, they have to be able to tell when advanced testing is needed on a particular stone.

This is because of the way the industry has changed in the past decade. Since the start of the new millennium, new treatments have become available for stones that until recently were thought impossible. Heat treatments of various kinds of stones, including diamonds, copper, rubies, and beryllium have made it more and more difficult to tell the difference between stones of true quality, and those that have been doctored to make it look like they are of that quality.

While the most advanced equipment is required to know for certain if treatments have been applied, in most cases it is sufficient to have the standard battery of gemological testing equipment--the difference is the knowledge base that is now required. Being up to date on the latest developments is of paramount importance.


Ideally, gem manufacturers and dealers are supposed to disclose the treatments undergone by a gem clearly so that the customer knows just what they're getting. Of course, this does not always happen. It is tempting for gem manufacturers--and for dealers as well--to try and pass off heat-treated or irradiated gems as natural ones; naturally clear and pure gemstones still take higher prices than artificially enhanced ones, as you might guess.

One of the problems is that there remains no global standard regarding just how gem treaters should tell their clients what they have done to a particular gem. Everyone in the industry--everyone honest, anyway--agrees that they should be disclosed, but they have yet to come to a consensus as to just how. Fortunately, most countries have standard systems that apply only to them, and that are available to anyone who's interested in learning more about them.

Types of Enhancement: Heat Treatment

This is by far and away the most common form of stone enhancement--it is practiced worldwide by nearly every major gem lab. And most of the time, it is readily detectable with standard equipment. Of course, there are those rare cases where advanced instruments are required, but thermal treating is an old technique, and one most gemologists are used to seeing.

Diamonds in particular have seen huge advancements in the treatments available for them. Off-color diamonds have long been a problem for the industry, but in 1999 that changed when high-pressure, high-heat treatments (HPHT) became available. The technique was advanced in the 2000s, as were the methods for detecting it. Today, the treatment is so advanced that it can produce virtually any shade of diamond desired, including black--and can remove colors from diamond, leaving the traditional colorless hue typically associated with diamonds.

Today, the process is so widespread, that color-enhanced diamonds are everywhere all over the world, and have become the norm rather than the exception in the case of many laboratories. Fortunately, research has revealed that a certain rather obvious method exists for determining whether a diamond has been color-treated. For reasons that are not well understood, most of the colorless treated diamonds are of type IIa, while 99% of all natural gemstones are type Ia. A simple test using very basic gemological equipment can determine of which type a colorless diamond is, and thus whether it is likely to have been color-enhanced.

Types of Enhancement: Diffusion Treatment

This is a more problematic form of enhancement to detect among colored stones, and posed a major problem for gemologists over the course of the 2000s. While identification is possible by looking at color concentration near facet junctions (it will be much higher in treated diamonds), most normal detection methods are general indicators rather than conclusive proof.

Sapphires, in particular, have suffered because of the prevalence of treatment with beryllium--which normally causes an orange color, but can be used to cause almost any color--and titanium--which causes a blue color. Treatment with these elements means that lower-quality sapphires can be changed to unusual colors and sold at a higher price.

And detecting these treatments--especially beryllium--proves very difficult. While with immersion techniques, where the stone is immersed in a certain kind of fluid and the way light refracts through it is analyzed, can detect titanium diffusion--which only changes the color of the surface of the stone--beryllium, a small atom, can enter through diffusion treatment all the way to the center of the stone. But it does leave occasional surface-level defects that can serve as evidence of, if not proof of, diffusion treatment.

Types of Enhancement: Clarity Enhancement

This proved to be one of gemology's largest challenges during the 1990s, though it has not proved such a problem since that time. Most clarity enhancement with diamonds involves a process called fracture filling--where imperfections in the diamond are quite literally filled in with tiny amounts of glass. This process makes the diamond look good, until a customer brings their jewelry in for repair. When heated to the intense temperatures required by some jewelry repair techniques, the glass melted and came out of the diamond, and customers were dismayed to find that they'd bought a far less valuable stone than they'd believed.

Better methods came along later, but they still were subject to scarring from basic jewelry repair techniques, even when they were done by master jewelers.

Most techniques involve laser drilling a diamond and filling it with acid to close the hole. However, this does leave a telltale mark on the surface of the diamond. A technique was developed in Israel that left no such hole, but it entered the market secretly, and because of this, was subsequently banned in Israel.


So far as is known in the majority of the modern gemologist community, most major techniques for artificially enhancing stones has been discovered and is publicly known. Disclosure works, and most honest dealers will disclose anything done to their gems.

But there's always that chance, and gemologists will have to continue to work hard to detect newer and newer techniques as they become available, and dishonest dealers try to pass off imperfect stones as perfect ones.

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