There are usually five kinds of the most precious gems in the world, which are called five treasures. They are: diamonds, rubies, sapphires, emeralds and golden-green cat's eyes.

However, some of these five kinds of gems are even rarer, such as colored diamond, pigeon blood red ruby, cornflower sapphire, Kashmir sapphire, Alexander variable stone and Alexander variable stone cat's eye. These gems are too rare to be labeled in categories, but they are even rarer and more precious in the international jewelry industry and the actual jewelry history.