A Beginner’s Guide To Common Gemstone Heat Treatments

Gemstone heat treatments can increase the beauty and value of many rough pieces. Learn how to conduct the most common procedures safely.

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A Note on Corundum Heat Treatments

Ruby and sapphire are some of the most commonly heated gemstones. However, I don’t discuss these gems in this article. A standard electric oven can’t reach the temperatures needed to treat these corundum gemstones. A special oven with platinum elements or another method of heating is needed. Heating corundum also requires controlling the atmosphere inside the heating chamber. Even with this special equipment, there are many subtle variations in technique.

There’s no simple approach to heating all the varieties of corundum. Gem material from different localities needs to be treated differently for successful results. Treating rubies and sapphires is a matter for experts.

Ovens for Gemstone Heat Treatments

The best tool for heating gems is a computer-controlled burnout furnace. It allows for very gradual changes in temperature. This reduces thermal shock, which can destroy some gems.

If you don’t have access to a computer-controlled oven, you can try other methods. However, you’ll then have to restrict yourself to treating gems that aren’t heat sensitive. Simply burying gemstone rough in sand and slowly and carefully changing the temperature in an oven will work in some cases.

Small lots of rough can be heated in…

Donald Clark, CSM IMG

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters “CSM” after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff’s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book “Modern Faceting, the Easy Way.”

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