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Trends in gemstones and treatments

Trends in gemstones and treatments

13 January 2015

By Cynthia Unninayar

Prized for their unique character and intrinsic beauty, gemstones are a major part of today’s fine jewellery. They come in all types, sizes, shapes, and colours. And, sometimes to enhance their beauty, they are subjected to various types of treatments. To learn more about the ever-changing landscape of trends in gemstones and their enhancements, as well as other issues facing the industry, we visited the very modern and prestigious Gem and Jewelry Institute of Thailand (GIT, a public organization) during a recent trip to Bangkok. Here, we caught up with the very gracious and very busy Dr. Pornsawat Wathanakul, Director of the GIT.

Dr. Pornsawat Wathanakul
Dr. Pornsawat Wathanakul

CIJ TRENDS & COLOURS: As a gem expert yourself, and as Director of the GIT, what changes have you seen in the types of gemstones used in jewellery over the last few years?

Dr. Pornsawat Wathanakul: We have seen a shift in the nature of gems being used in jewellery. The most notable is the move towards what we might call a “natural” approach to gemstones. This started with the appearance of the so-called “sliced diamonds” that came to market several years ago. Lesser quality diamonds were cut into slices that clearly showed their inclusions and other “defects.” Jewellery designers were very creative in turning these “gem lemons” into delightful and delicious lemonade by actually highlighting the inclusions as something distinctive and individual to the stone. Surrounded by other gems or diamonds, these diamond slices became quite popular and appreciated in the world of fine jewellery.

Following the diamond slices, we now see more gem dealers slicing emeralds, sapphires, and other stones. These examples show the stones in their more “natural” state, you might say. Other gems moving into the world of fine jewellery are geodes, jasper, agates including dendritic agates, fossilized coral, various quartzes, and even “precious” stones in matrix set in creative designs. But, the precious and rare gems still remain highly prized by jewellers and consumers.

Over the last few years, we have seen increasing interest from China, traditionally a jade market, for coloured stones, but especially Pigeon’s Blood rubies and Royal Blue sapphires.

GIT has an impressive array of advanced equipment in its gem testing section.
GIT has an impressive array of advanced equipment in its gem testing section.

What gems come mostly to GIT for analysis and certification?

As a national institution for gem testing, we serve the entire supply chain for the gem and jewellery sector. We test all kinds of gemstones, whether rough, faceted, or mounted, as well as pearls. The majority, however, are from the corundum family, namely ruby and sapphire. GIT also tests precious metal alloys for their content and for Hallmarking purposes.

In touring your facilities, the lab seems to be quite cutting-edge, with rooms full of advanced testing equipment…

The GIT was established in 1998, and is one of the world’s seven leading laboratories that are members of the Laboratory Manual Harmonization Committee (LMHC). We have advanced equipment that includes a variety of specialized instruments, spectrometers, and X-ray units that are used to distinguish between natural and synthetic gems, to grade diamonds and pearls, distinguish natural from cultured pearls, determine the geographical origin of gemstones, and detect treatments in coloured stones, diamonds, and pearls. GIT has also researched the master sets of Pigeon’s Blood ruby, Royal Blue sapphire, and Cornflower Blue sapphire. The institute also conducts training in the gems and jewellery sector as well as related activities.

[Editor’s note: The other six members of LMHC are CGL (Japan), CISGEM (Italy), DSEF (Germany), GIA (USA), Gübelin Gem Lab Ltd. (Switzerland), and the SSEF (Switzerland).]

Examples of unheated rubies (left) and after heat treatment (right).
Examples of unheated rubies (left) and after heat treatment (right).

What is the most common type of gemstone “enhancement” and how can it be detected?

Hundreds of years ago, people discovered that they could change a gem’s clarity and colour by heating it. Today, the vast majority of gemstones are heated. The most common stone to undergo heat-treatment is amethyst. Pale purple amethyst can be converted to yellow-orange citrine by heating. Other stones that are heat-treated to improve quality include ruby, sapphire, morganite, kunzite, zircon, and tourmaline. After being subjected to heat, tanzanite, for example, turns to a lovely purplish-blue, while aquamarine intensifies its blue hue. Sapphires are heated to intensify or lighten their colour and improve uniformity. For ruby and sapphire in particular, special heating techniques have been developed through experimentation to best suit the particular type of stone. Today, out of 1,000 sapphires, less than one is unheated, which makes the untreated gems rare and very valuable. The most important technique used to tell if a stone has been heated is by microscopic observation of its inclusion features, which are changed as a result of the heat.

Faceted sapphires that have been beryllium-diffused to improve colour and clarity.
Faceted sapphires that have been beryllium-diffused to improve colour and clarity.

Can you elaborate on beryllium diffusion in sapphires?

In beryllium diffusion, sapphires are heated to high temperatures in the presence of the light element beryllium (Be), which penetrates deep into the stone and helps modify the appearance by making the colour more uniform and, in the case of dark blue sapphires, by making them lighter. This treatment is also used to introduce yellow colour into natural white sapphires by producing colour centres together with iron. This yellow has also been introduced into pink sapphires, which then take on the lovely pink-orange shades of Padparadscha. Once considered controversial, Be-diffusion is now generally accepted because of the beauty it produces in the gems and their colour stability.

This treatment can be detected by analyzing the Be content in the gemstone using advanced techniques such as Laser Induced Breakdown Spectrocopy and Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Because the stone undergoes high temperatures for a long period, its internal features will also be significantly damaged, providing additional confirmation of the Be-treatment.

We hear a lot about lead-glass filled rubies. Is there a way consumers can tell if the stones in their jewellery have been "enhanced" in this manner?

Glass-filled rubies have been around for decades and are now widely used for low-end jewelry products. Basically, glass mixed with lead or bismuth is filled in cavities or fissures in a ruby to disguise the imperfections and improve colour and clarity. The problem with this treatment is that the glass filler is not durable and as it deteriorates, the appearance of the stone can change. It is important that the customer be informed about this treatment and how to care for the stones.

The consumer can often distinguish this treated stone with a 10x loupe. Commonly, the stone will display a very clear purplish, bluish, or pinkish flash effect while moving it. And, many flattened and trapped gas bubbles are also usually seen. The extent of the treatment varies depending on the nature of the original material. If readers are interested in this topic, they can find more information on the LMHC information sheet number 3, on the website,

Most gemstones are treated in one form or another. Of 1,000 sapphires on the market, less than 1 are unheated. Shown here is an example of a rare unheated sapphire.
Most gemstones are treated in one form or another. Of 1,000 sapphires on the market, less than 1 are unheated. Shown here is an example of a rare unheated sapphire.

Do you find gems that are purportedly authentic, but turn out to be man-made synthetic stones?

Rarely, but yes. Some months ago, a client brought in two beautiful rubies that had been certified natural by another lab, but the owner still had a doubt. Our experts analyzed the rubies and found them to be, in fact, synthetic. There are also occasions when two labs will disagree on an analysis of a gemstone, and the GIT is called in to provide a third opinion.

What are some of the other issues facing the gem industry?

There are the issues of synthetic diamonds being passed off as natural, and increasingly we are seeing synthetic corundum being sold as natural ruby. In some cases, the synthetic corundum has even been fracture-filled with lead glass. This may sound ridiculous at first. Who would want to go to the trouble of fracture-filling a man-made stone? But, it is a way to make people think the synthetic is a lower-quality natural stone, which is comparatively still more valuable.

Unfortunately, as gemstone prices rise, there will be people who want to cheat. It is important for customers to understand what they are buying and to purchase from reputable dealers. And, it is important for dealers to disclose any treatments their stones have been subjected to.

As I mentioned earlier, most gems are enhanced. This is not a bad thing as these stones provide less expensive alternatives to consumers as well as colours that don’t exist in nature. The key word is disclosure and that is good for the entire industry.

As part of its mandate, GIT tests not only gems and pearls, but also precious metals.
As part of its mandate, GIT tests not only gems and pearls, but also precious metals.

Buying gemstones and jewellery with confidence - 28 January 2013 provides the global jewellery markets with the latest jewellery, haute joaillerie and luxury creations, all the news and decisive trends and colours in fashion. Europa Star - CIJ Women’s Watches & Jewels - the Trends & Colours magazine, is circulated worldwide to reach the top international retailers and end buyers of fine jewellery in more than 100 countries.
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