How to Test for Diffusion Treated Gems

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Step 3: Practical Gemology

Lesson 16

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diffusion treated gems - untreated blue sapphire
On the left, a natural, untreated blue sapphire. On the right, that same sapphire immersed in methylene iodide.

Since diffusion treated gems are so common, gemologists must learn how to identify these treatments.

Diffusion treatment usually involves applying color to a colorless cut gem by introducing chemical impurities at an atomic scale. Some sapphire gems receive this treatment to improve their color. We gemologists now face a new beryllium/lattice diffusion process that appeared on the market in 2002 involving padparadscha sapphires. However, we can detect it using established methods for identifying diffusion treated gems.

The Immersion Method for Identifying Diffusion Treated Gems

Setting Up

This inspection process is simple. First, you need a substage, diffused light source. A microscope, polariscope, or even a flashlight will do. If you don’t have a …

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