JADE

Jade is a name applied even by scientists to two different minerals: JADEITE and NEPHRITE, which are made up of compact crystal fibres or little grains. In 1863, French scientist Damour demonstrated that these two were utterly different minerals, although their appearance and characteristics seemed to be the same. Both are more resistant than steel, but their hardness is limited. This is the reason why they have been used ever since the Neolithic to make weapons, tools, sculptures, and jewels. The Chinese call "jade" any green stone which is not transparent. They were widely used by pre- Columbian civilizations in Central America.

JADEITE is a sodium- and aluminium-rich pyroxene. It has a Mohs hardness of 6.5 - 7.0, with a relative density of about 3.3. It is monoclinic, and comes up in the form of aggregates made of fine fibres and tangled grains. It may come in different colours apart from green, such as purple or orange, but the most prized variety is Imperial Jade, which is characterized by an emerald green colour (due to chrome) and by its semi-transparency. Its polished surface often looks like "orange skin", due to the different hardness of its component grains. This only adds to the beauty of the material. It is found in Burma, Guatemala, and California, among other places.

NEPHRITE is a calcium- and magnesium-rich amphibole mineral with iron content. It has a hardness of 6 - 6.5, with a relative density of 2.9 - 3. It is monoclinic, and comes up in the form of aggregates made of fine fibres. It is green (may come in all shades of green, but olive-green is the most common) and has some characteristic black spots.

On the other hand, there exists another mineral with an appearance which is very similar to that of the abovementioned that also has analogous gemmological characteristics. In the trade it is known as INDIAN JADE. It is in fact a variety of quartz called "AVENTURINE", which is green due to a number of minute mica inclusions. As it belongs to the quartz group, this mineral has a hardness of 7, with a specific gravity of 2,65, and it is trigonal. Indian jade has all the good qualities of quartz, such as resistance. It communicates energy and has protective powers against adversity. This variety in particular brings good luck for work and gambling.