High-grade gems: including diamonds, rubies, sapphires, emeralds, golden-green cat's eyes, variable stones and high-grade pearls. Among them, diamonds, rubies, sapphires and emeralds are called gems by western countries. Diamonds are the king of jewels.
Intermediate gems: including aquamarine, tourmaline, zircon, spinel, etc. , are more common. Grade pearls, jadeite and opal are also classified as middle-grade gems.
Low-grade gems: including turquoise, topaz, amethyst, olivine, topaz, sapphire and other varieties.