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giovedì 28 giugno 2012

Jade: Jadeite and Nephrite


This stone had for thousand years a great significance specially in Asia.

It always been source of inspirations not only as material for art craft, but also for spiritual and religious meaning. In Asia, but mostly China, Jade has a very long tradition either  for weapons, tools, jewellery, ornaments and sculptures. Archaeologist found jade’s art craft even older than 7000 years ago.





In the past, the people use to be confused about jade; the word "jade" has been used to refer a two different minerals: jadeite and nephrite. Those material have a chemical composition very different from each other, but both are soft enough to be carved and tough enough to resist to impacts.




Chemically are very different, they belong to 2 different mineral species. In the trade the value of jadeite is way higher than nephrite, and it’s 3 most important qualities are: color, transparency and texture


Anytime we talk about jade, we think about a green stone, but actually jadeite comes in other colors, yellow red orange white brown gray black and lavender, which is the second color most popular. Of course, the green color is the most requested in the marked, the most valuable is an uniform intense green and high saturated, called imperial green, which is very rare.


white jade
lavender jade

black jade

orange jade













imperial green jade


















The green color is caused by the presence of chromium, the same element that causes the color in emeralds.
Usually, black jadeite is carved, but starting from the 2000 Guatemala’s black jadeite began to be used also as gem in jewellery.

Of course, in the marked is more requested a jadeite with the best uniform color, so uneven colored stones are carved in statues and tools, and also cheap jewellery.







The transparency of the jadeite vary from semitransparent (which is the best) to opaque.



jade bangle




It texture can be from fine to coarse, depending on its crystal’s size. The crystal structure contributes to its texture and to its exceptional toughness. This is way is very often polished as beads, bangles or ring, one piece only, it very difficult find other stones with this properties.

jade ring









dyed jadeite


Treatments are widely common in jadeite: in the most used the jade is dip in melted wax to improve its luster and fill veins and pits. Other treatments are bleaching or dyeing the jadeite to enhance its color.
The sources of jadeite are several in the earth: the best quality comes from Myanmar, Guatemala is nowadays the major source of black jadeite, we have also in Russia and California.









nephrite
Nephrite is commonly called jade, just like jadeite, but this one have a completely different composition and structure, and is also widely common so it has a lower price.
Its color is less interesting than jadeite, usually darker, less uniform with low saturation. It’s rare see nephrite in jewellery, is usually used for carving tools and everyday objects.
Even for nephrite the sources are different in the world; the major are China, Canada and New Zealand.

nephrite






Be careful, because is an high requested gem, it easily switched with substitutes, those might have similar colors to the originals, but rather than this there are not other qualities like the original jade.
Serpentine










The most common substitutes in jewellery are Chrysoprase (a chalcedony variety) and green garnet; for carving is very popular the serpentine, called in the trade “Korean jade”.