Gemstones, including rubies, emeralds, and sapphires, can be sold for cash, much the same as diamonds and other jewelry. However, more often than not, those stones have very little resale value ...

A 10.3-carat fancy vivid blue diamond, "The Mediterranean Blue," mined from South Africa's Cullinan mines, sold at auction in Geneva for $21.5 million, slightly above its estimated value.