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A common treatment for applying colour to or enhancing coloured gemstones.

Coloured gemstones have undergone treatment for thousands of years. As long as the treatment is permanent, it is widely accepted that the role of enhancing Mother Nature’s treasures is important for maintaining the popularity of genuine gemstones.

To best understand diffusion, first of all let’s remind ourselves that most gemstones are “allochromatic” (see section earlier in this volume), meaning they receive their beautiful colours through the presence of impurities. For example, Beryl is a colourless gemstone until impurities are present: iron turns the gem into an Aquamarine; chromium and vanadium turn the gem into an Emerald; and the presence of manganese creates Morganite.

One of the oldest treatments of coloured gemstones is heat treatment, whereby rough gem material is heated to extremely high temperatures in order to continue the work of Mother Nature. Virtually all Sapphire and Ruby on the market today is heat treated.

Diffusion is a technique whereby certain natural elements, those used in nature when colouring allochromatic gems, are placed on the surface of the gem during the heating process and the colour is diffused into the gem. The treatment is permanent, however the colour created through diffusion normally only penetrates a small distance within the gem. Therefore if the gem is chipped or re-cut, the less vivid colour underneath will be visible.

One of the latest developments in diffusion treatment is from a company in India; the company is a partner of The Genuine Gemstone Company and shares the same office complex in Jaipur as the team at GemCollector. This new technique uses thin film thermal technology to diffuse the colour deeper into the gemstone, making its beauty more resistant to chips and knocks.

The technique has just received a U.S. Patent and is widely used by many of the brands within the Gems TV portfolio. This research has also led to some amazing new colours in Topaz and Quartz and these can be recognised by the names “Spice Topaz” and “Spice Quartz”.

One of the most common treatments of diffusion is with Star Sapphires and Star Rubies, where the treatment is used to enhance the beautiful asterism effect.

Beryllium treatment and cobalt treatment are other forms of diffusion. And when buying Sapphires and Rubies, unless stated otherwise, it is safe to assume that that the gem has most likely undergone some form of diffusion in order to enhance their vivid primary colours.

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Rubies and Sapphires are often diffused.