With rubies commanding much of the colored gemstone market, treatments to enhance their color and clarity were developed early on in an attempt to be more desirable and fetch more money. Early in the history of rubies, treatments were established and they have only been improved upon over time with new technological innovations.
It is important to understand the types of treatments and enhancing techniques that can be performed on rubies so that you are able to ask the correct questions and make an informed decision around a ruby purchase. In this article, we break down the three most common forms of ruby treatment or enhancement, and what it means for the gemstone’s value and durability .
The oldest and most common ruby enhancement is heat treatment. Today, the majority of the rubies in the marketplace have been heat-treated or thermally enhanced. Heat treatment is used to improve a ruby’s color, remove color zoning , and improve clarity.
Over the last couple of decades, high temperatures in excess of 1700 degrees Celsius have been applied, which improves clarity by dissolving silk as it improves the color. The results can be dramatic: rubies from Sri Lanka become more intense red, gems from Thailand lose their brownish color, and Möng Hsu rubies from Myanmar lose their dark cores.
Because silk crystallizes at lower temperatures, when corundum is heated to between 1200-1600 degrees Celsius, star rubies can be created or improved. Gem connoisseurs prize those rare stones that show fine color and clarity without this form of enhancement.
The clarity of a ruby can be compromised by surface reaching cavities or fractures. Many rubies been heated in the presence of a chemical flux in order to improve their clarity, luster, and durability. At high temperatures, the flux melts and penetrates surface reaching fractures or cavities in the stone.
When cooled, the flux may either solidify into a glassy mass (lead filling) or facilitate corundum re-crystallization within the fissure (flux healing). There is considerable debate in the industry about how much of the clarity enhancing effect is due to filling versus healing, but in either case, the treatment can make low value, poor quality rubies much more marketable.
Flux enhancements have earned a bad reputation because in extreme circumstances, poor quality gemstones are quite literally held together by the glassy filler. These glass or glass-filled rubies can also be extremely fragile. Many are destroyed during the jewelry repair process, routine cleaning, or even re-polishing.
Diffusion processes, including both titanium and beryllium treatments, are relatively new techniques that have generated a great deal of controversy in the gemstone industry. Although diffusion treatments have several variations, rubies are typically heated to very near their melting point in the presence of color-inducing elements, which penetrate or diffuse some distance into the stones.
In the case of titanium diffusion, for example, a layer of strong color is created near the surface of a poorly colored stone. Because the layer of color is restricted to the surface of the stone, the original weak color of the stone can be revealed if it is chipped, nicked or re-polished.
Diffusion treatment is often the last resort when heat treatments have failed to enhance the color of a stone. Rubies that have obtained their color from diffusion treatments have little intrinsic value. Reputable dealers will identify diffusion-treated rubies and offer them at prices well below those of natural, untreated stones.
Aside from treatments, or enhancements, emeralds have also been simulated in labs. We explore that process and what you need to know next with Ruby Simulants & Synthetics.