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Since the supply of fine quality rubies and sapphires is limited, many techniques have been developed to enhance their appearance. In fact, no other gem species is subjected to as many types of treatment as corundum. Heat treatment is accepted as a common practice and has little effect on value, where other treatments have considerable impact. Some rubies are worth as little as 5% of similar appearing, untreated gems.
Some of the treatments are very subtle, invisible even with a loupe or microscope. To make matters worse, many treated rubies and sapphires will have natural inclusions. You have to examine them very carefully to tell if they are treated or not. Taking the …