A Gemstone's Journey: 3. Heating of Sapphires
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Heat treatment is a common practice in the gemstone industry, particularly for Sapphires and Rubies. This process involves heating the gemstones to high temperatures in order to improve their color, clarity, and overall appearance. The heat treatment process can vary depending on the type of gemstone being treated and the desired outcome.
There are several different types of heating methods that can be used to treat sapphires, each with its own benefits and drawbacks.
- Conventional Heat Treatment:
Conventional heat treatment involves heating the sapphires in a furnace to temperatures of up to 1,800 degrees Celsius. This process can take several hours to several days (and even months), depending on the size and quality of the sapphires. The heat treatment process can improve the color of sapphires by removing or reducing the presence of iron and titanium impurities, which can give the gemstones a cloudy appearance. The heat also causes the silk-like inclusions in the sapphires to dissolve, resulting in a clearer and more transparent gemstone.
- Low-Temperature Heat Treatment:
Low-temperature heat treatment involves heating the sapphires to temperatures between 1,000 and 1,200 degrees Celsius. This process is typically used to improve the color of sapphires by removing or reducing the presence of iron and titanium impurities. Low-temperature heat treatment is less aggressive than conventional heat treatment, and can be a good option for sapphires with delicate inclusions that could be damaged by high temperatures.
- Flux-Heated Treatment:
Flux-heated treatment involves heating the sapphires in a mixture of flux and chemicals, which can alter the color and clarity of the gemstones. This process can be used to improve the color of sapphires that are too light or too dark. Flux-heated treatment can also be used to dissolve inclusions in the sapphires, resulting in a clearer and more transparent gemstone.
- Diffusion Treatment:
Diffusion treatment involves heating the sapphires in the presence of chemicals, which can alter the color of the gemstones. This process can be used to create sapphires with unique colors, such as yellow or orange. Diffusion treatment can also be used to create bi-colored sapphires, which have different colors on different sides of the gemstone.
- Irradiation Treatment:
Irradiation treatment involves exposing the sapphires to radiation, which can alter the color of the gemstones. This process is typically used to create blue sapphires, which are not naturally occurring. Irradiation treatment can also be used to create other colors, such as green or yellow.
In conclusion, sapphires can be treated using several different heating methods, each with its own benefits and drawbacks. Conventional heat treatment is the most commonly used method, and can improve the color and clarity of the gemstones. However, low-temperature heat treatment, flux-heated treatment, diffusion treatment, and irradiation treatment can also be used to create unique and desirable sapphires. It is important to note that the process of heat treatment should only be performed by experienced professionals to avoid damage to the gemstones.