How Many Different Types of Precious Gems Are There On Earth?

Gems are valuable, but some are much more valuable than others.

Such gems as topaz, aquamarine, and garnet are called semi-precious, and cost much less than precious gems.

There are only four minerals that are considered precious gems today: diamond, emerald, and two forms of corundum, ruby and sapphire.

Pearl, which is not a mineral but the product of oysters, is also called a precious gem.

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Karen Hill is a freelance writer, editor, and columnist for Born in New York, she loves interesting random facts from all over the world.