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Gem of the Month, Gemstones













L to R: Yewn High Jewellery earrings | Tiffany & Co. pendants | Wallace Chan brooch
L to R: Yewn High Jewellery earrings | Tiffany & Co. pendants | Wallace Chan brooch

Jade Part I: Jadeite

The lustrous texture and luminous colours of polished jade have been prized for thousands of years. Ancient cultures in North, Central and South America, New Zealand, Asia and Europe valued jade for its beauty, hardness and durability; properties that made it suitable for use in implements, jewellery, regalia and decorative items.

Wearers believed jade endowed them with long life, good health and fortune, and today jade jewellery still has strong traditional associations in many cultures.

The name ‘jade’ is the commercial term used for jadeite and nephrite. Despite their similar appearance, these minerals have distinct gemmological properties.

Both are silicates; jadeite is a sodium and aluminium silicate, while nephrite is a calcium and magnesium silicate.

Both are polycrystalline in structure, with many interlocking microscopic crystals, making them some of the toughest materials in the gem world.

So, what is the difference between the two? This month, we focus on jadeite.

Typically, the name jadeite is associated with a rich deep green colour, but the gem is found in many hues – pale green, deep green to black, shades of mauve and blue, as well as white, red, brown and yellow – and is often mottled. The richer and more even the colour, the higher the value.

In China, jadeite of fine green colour and translucency was once reserved for the Emperor’s court and is known as ‘imperial jade’.

‘Tomb jade’ is the name used for reddish brown jade, while ‘icy jade’ or ‘water jade’ denotes the colourless, almost transparent form of the gem.

Jadeite has a hardness of 6.5-7 on Mohs’ scale, making it suitable for use in a range of jewellery. However, it is the gem’s tenacity and capacity to be carved and fashioned, along with its vitreous lustre, that makes it attractive to jewellers and gem carvers.

As with many other gemstones, jadeite is treated to improve colour and lessen the appearance of blemishes.

A classification system based on the type of treatment applied to the gem is used to describe the quality (and hence value) of jadeite.

The system uses the letters A, B and C, and was developed by traders in Hong Kong where much of the world’s jadeite is traded.

‘A’ refers to untreated jadeite; however, it may be waxed and as this is a removable treatment that affects only the surface of the gem, it does not have to be disclosed.

‘B’ jadeite has been treated with acid to remove stains and noticeable inclusions. This treatment can damage the gem’s surface, making it fragile. Consequently, a further treatment using resin to impregnate the gem is used to enhance its durability.

The classification ‘C’ refers to ‘B’ jadeite that has been also been dyed to improve the gem’s colour.

Both ‘B’ and ‘C’ jadeite must be disclosed as treated gems.

Given that the prices of ‘A’ jadeite can be in the millions of dollars whilst ‘C’ jadeite can be a few dollars for the same sized piece, it is helpful to be able to distinguish between them!

There are many simulants sold as jadeite. Some gems that can look similar and are sold to confuse the buyer include bowenite, aventurine, prehnite, chrysoprase and chalcedony. Standard gem testing will identify simulants quite easily.

Key sources today of quality jadeite are Myanmar (Burma), Guatemala and Russia.

 

 

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ABOUT THE AUTHOR
Susan Hartwig

Susan Hartwig FGAA came late to the world of gemmology after a long career in corporate training and project management. She combines her love for writing with a passion for gems and jewellery. Susan writes regularly for her gemmology blog ellysiagems.com. For more information on gemmology courses and gemstones, visit: gem.org.au

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