The following information is from the website:- http://en.wikipedia.org/wiki/Jade
Jade is an ornamental stone. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:
Nephrite consists of a microcrystaline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour.
Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystaline interlocking crystal matrix.
The English word jade (as well as the English word "jadeite") is derived (via French l'ejade and Latin ilia[1]) from the Spanish term piedra de ijada (first recorded in 1565) or "loin stone", from its reputed efficacy in curing ailments of the loins and kidneys. Nephrite is derived from lapis nephriticus, the Latin version of the Spanish piedra de ijada.[2]
Nephrite and jadeite were used from prehistoric periods for hardstone carving. Jadeite has about the same hardness as quartz, while nephrite is somewhat softer. Both nephrite and jadeite are tough, but nephrite is tougher than jadeite. They can be delicately shaped. It was not until the 19th century that a French mineralogist determined that "jade" was in fact two different materials. The trade namejadite is sometimes applied to translucent or opaque green glass.
The hardness (Mohs scale) : 6.5
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