Heat treatments, wrongly construed as being artificial, mirror the exact same processes that occur in nature. In today’s gem and jewelry industry heat treatments that have proven to be stable are widely practiced and accepted.

Ever since demand grew Sapphires have been artificially treated to improve their color and clarity. In fact it is safe to say that 99% of all Sapphire gems, which are processed and cut today have been subjected to some form of heat treatment.

Corundum, whether Sapphire or ruby, is routinely heated at temperatures that range from anywhere between 700 to 2000 degrees Celsius. Modern heating units reach temperatures close to the melting point of corundum: 2050 degrees Celsius.

Depending on the required effect, heating is carried out in either an oxidizing atmosphere or a vacuum atmosphere:

• An oxidizing atmosphere requires the presence of oxygen. This method is employed to lighten the color of Sapphire by decreasing the dark blue color. It is also used to eradicate the blue element of purplish rubies, leaving the red color caused by chromium unaffected.

• A vacuum-reducing atmosphere requires the presence of carbon monoxide and the absence of oxygen. This form of treatment is used to intensify the blue color in Sapphire. Previous to this treatment many white to pale blue gemstones were considered valueless until this practice was discovered.

An additional technique used in treating Sapphire is the ‘Diffusion’ treatment, which involves heating pale or colorless Sapphire to a very high temperature while it’s in contact with chemical coloring agents. This creates a layer of color that’s usually less than 1/100 inch thick. Diffusion color can be removed by repolishing or recutting. Otherwise, both treatments’ effects are normally permanent, and they create no special care requirements for gem owners.