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: Sapphire Color Enhancements

Sapphire Enhancements & Treatments

The process of heating sapphire and other gemstones to enhance their color is not a new phenomenon. Sri Lanka has a long year history of heating rubies to enhance the reddish-pink color, and remove any unwanted bluish or purplish hues, and sapphires were heated to increase the intensity of their blue color. Sri Lanka's gem "burners" traditionally apply heat treatment using a blow-pipe and charcoal burner, to super-heat the stone.

Many of today's commercially available sapphires have had some type of color enhancement, and there are several processes that are considered to be unethical practices by today's standards - especially if they are not disclosed to the potential buyer. These methods include the "beryllium diffusion," "deep diffusion," or "lattice diffusion," process which use a combination of iron and titanium powders which are heated to 2,000 degrees Celsius to change a natural pale-blue or colorless sapphire's color into an intense deep blue color. The beryllium diffusion process is also used to enhance the yellow or orange-yellow color in Padparadscha-colored Ceylon sapphire.

Under microscopic inspection, a heat-treated Sapphire can often be identified by its characteristic inclusions known as "decrepitation feathers," and small by observing "discoid fractures" which congregate around natural mineral inclusions.

Color Treated Sapphires - Photo: Dan Dennis

Heated Pink Sapphire Inclusions (Photo: © AGSL)

Sapphire corundum is often heat-treated in a high-vacuum, high-temperature environment while applying a combination of chemicals such as beryllium, boron, cobalt, and magnesium. By lengthening the time that a stone is heated, and/or by increasing the treatment temperature you would increase the intensity and depth of color, while also increasing the unwanted telltale inclusions. That is why there is a balancing act between the benefits of color improvement, and the risks of damaging the gem altogether.

Today, much of the pink, blue, and yellow sapphire that has originated from countries such as Madagascar or Sri Lanka (above, left) are heat-treated in Thailand and Sri Lanka before being exporting to Europe and America. Pale yellow Sapphire originating from Thailand may be heat-treated to produce an intense canary-yellow, golden honey, or deep orange-yellow color. Colorless sapphire from Sri Lanka, which is known as "geuda" is commonly heat-treated to produce a bright-blue pastel color.

Due to the frequency and high probability that some type of enhancement has been applied to most sapphire gemstones, a specimen that is certified by a gemological testing lab as "natural," unheated sapphire will usually sell for four to five times the price of its heat-treated equivalent.

Synthetic Sapphire

Synthetic corundum (sapphire or ruby) was one of the first gemstones to be reproduced by artificial means, using the "flame-fusion" method (aka Verneuil Process) which was invented by French chemist Auguste Victor Louis Verneuil, in 1902. A diamond simulant which gained popularity during the early 1900's was known as "Diamondite," but was actually a synthetic colorless sapphire produced by Verneuil's flame-fusion method. The Verneuil Process has been replaced by the "Flux-Grown" method which still produces high-quality gem-grade sapphire.

Synthetic blue sapphire is currently being produced by Chatham Created Gems in San Francisco, California. Synthetic star sapphire was developed in the late 1940's by Union Carbide under the name "Linde Stars," and synthetic star sapphire is currently being produced by Nakazumi Earth Crystals in Osaka, Japan.

When seen by a trained observer, a jeweler's loupe can reveal the difference between the characteristically straight growth-lines that are found in natural sapphire, and the curved growth lines which are found in synthetic sapphire. By using a microscope, synthetic sapphire can be identified by observing characteristic inclusions or feathers which are a byproduct of the synthesizing process.

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Sapphire Gemstones