The only “precious” gemstones are diamond, ruby, sapphire, and emerald. All other quality stones are called “semiprecious,” even though they may not be any less valuable or beautiful.

The five traditional cardinal gems are:
amethyst (purple) – Rare and precious in the Old World until large deposits were found in Brazil.

Diamond (transparent)

Emerald (green)

Ruby (red)

Sapphire (blue)