Jewellers' Network

Jade, it’s varieties, substitutes and stimulants

Jade is a term used to describe two physically similar but chemically very different stones.

Whereas nephrite is a silicate of calcium and magnesium, jadeite is a silicate of sodium and aluminium. Sir Charles Hardinge, author of Jade Fact and Fable, proposed the names ‘amphibole jade’ for nephrite and ‘pyroxene jade’ for jadeite. While his suggestion was obviously meant to clarify the different nature of these materials it did not receive wide acceptance.

Jadeite generally exhibits cleaner brighter colours. It has a higher refractive index and is slightly harder and heavier than nephrite.

The circular perforated disc that occurs frequently in Chinese jade carvings is the symbol for the deity “Heaven”.

Bats are commonly encountered as a decorative feature and they symbolize “Happiness”.

Fish are used as a symbol to indicate “Power and Rank”. The Cicada is a symbol of resurrection (similar to Egyptian scarab).

The Dragon is a symbol of clouds, thunder and rain.

An attractive combination of jadeite and albite feldspar, “Maw-sit-sit” is a desirable carving material that is found in upper Burma (Myanmar)

Chloromelanite, a very dark green jadeite was used for tool making in ancient times but it is seldom seen as an ornamental material.

Hydro-grossular garnet or “Transvaal Jade” was highly valued in China as a jade substitute. Heavier, brighter, just as hard and carving as well as jadeite, it is not surprising that the deposit in the Bushveld Igneous Complex near Brits has been virtually worked out.

Bowenite and williamsite are termed precious serpentines in China where they are carved into sizable artefacts such as incense burners, statues and representations of the phoenix.

Such pieces are generally traded as “New Jade”.

Chrome chalcedony was first discovered in the Great Dyke of Zimbabwe (Rhodesia) by Mac McLean, who was the mining engineer at the Mtoroshanga Chrome Mine.

Mac was a keen rockhound and he had soon cut a range of fine emerald green cabochons from the material. They found a ready market under the trade name Mtorolite.

When he sent some of the rough to China for carving it produced some magnificent pieces. A pair of fine screens comes to mind. This created an immediate demand for a steady supply of the rough from the jade factory in China that had worked on it.

The material displayed an intense red under the Chelsea filter so it was not long before some of the very fine green highly translucent material was being facetted and finding its way into the market as emerald.