‘Jade’ actually applies to two different rocks that are made up of different silicate minerals. These are jadeite and nephrite. The distinction between jadeite and nephrite has only been made since the early 19thC, since they are extremely similar in appearance, hardness and malleability. Their colours do differ, however – nephrite ranges mainly from mid- to dark-green or grey-green, but can also be white, yellowish or reddish, whereas jadeite can also be green but is more often found in whites, pinks and reds, blacks, browns and violets. Creamy white jade is known as ‘mutton jade’ in China, while the beautiful emerald green variety is known as ‘kingfisher jade’. In both nephrite and jadeite, the way the colour is distributed varies a great deal and only the very finest jade has an evenly distributed colour. Collectively, jade is about as hard as quartz, exceptionally tough, beautifully coloured and as such, can be ornately carved and shaped.
The English word 'jade' is derived from the Spanish term piedra de ijada (first recorded in 1565), meaning 'loin stone', to refer to its reputation for curing ailments of the loins and kidneys.
During the Stone Age of many cultures, jade was largely used for weapons such as axe heads and knives. It was particularly suitable for this as it is stronger than steel. As metal-working technology advanced, jade's beauty made it valuable for ornaments and decorative objects.
Kingfisher jade was the most popular gemstone amongst 19th Century Chinese imperial scholars and rulers. It was known in China as yu,or the ‘royal gem’ from as early as 3000 B.C. As well as decorative ornaments, jade was used in grave furnishings for high-ranking members of the imperial family. Its value and usage in China is roughly comparable to that of gold or diamonds in the West. Yearly tribute payments made to the Chinese Imperial Court often consisted of the most precious white jade. These were then formed by skilled craftsmen of the Court into objets d’art. A visit to a jade market in Asia, be it in Hong Kong or in Rangoon, or to a Hong Kong jade auction organized by Christie’s, gives an indication of just how important this gem is to people in Asia.
Jade is also popular in New Zealand, particularly in Maori jewellery. It is referred to simply as greenstone.
Since jade, as a rule is not transparent but has a fine luster, it is usually considered best presented in the cabochon form. It is also popular in thin slivers worn as pendants and bracelets.