Destructive Gemstone Tests: Hot Point Testing

Step 3: Practical Gemology

Lesson 21

When subjected to a hot point test, real coral releases a smell like burning hair. Hot point testing is a last resort destructive procedure gemologists can use to determine if a piece is a plastic imitation. “Large pieces of coral” by Connie Ma is licensed under CC By-SA 2.0

Hot point testing can determine if a gem material is natural or a plastic imitation. It can also reveal if a stone is treated with wax or plastic. You can purchase electrically heated hot points or you can make your own. Just insert the blunt end of a needle into a cork. To use, simply heat the needle over a small flame until the tip turns a dull red.

Heavy Liquid Warning

Do not use heavy liquids on a gem before hot point testing. In fact, it’s not a …

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