“Jade” is a generic term for nephrite, jadeite, and under certain conditions green omphacite. In China, a pierced jade disk is a symbol of heaven.

In the world of gemmology, jade traditionally encompasses two primary materials: jadeite and nephrite. Recently, some green omphacite has also been included in this category. These materials are metamorphic rocks composed of tightly interlocking mineral crystals, which contribute to their exceptional toughness.

Jadeite can range from semi-transparent to opaque and is available in a broad spectrum of appealing colours. These include various shades of green, yellow, reddish orange, as well as white, grey, black, brown, and lavender (often a light purple or greyish violet). The colour distribution in jadeite can be uneven, creating an intriguing visual texture that carvers use to craft imaginative and captivating designs.

Nephrite, on the other hand, ranges from translucent to opaque and displays colours such as light to dark green, yellow, brown, black, grey, or white. Its hues are generally more subdued compared to those of jadeite.

Omphacite, traditionally recognized as dark green to black, has shown some green varieties in GIA laboratories that closely resemble fine green jadeite in colour and gemmological properties. Identification of omphacite requires advanced testing techniques, such as Raman spectroscopy.

Today, gemmologists often use the term "jade" as a broad descriptor for nephrite, jadeite, and, under certain conditions, green omphacite. The term “Fei Cui” is a traditional Chinese name for jadeite but is not universally accepted; it is commonly used in various parts of Asia to refer to jadeite, kosmochlor, and omphacite.

Throughout history, the term jade has sometimes been incorrectly applied to various gems and ornamental materials that resemble jade, including some manmade substitutes.