Jade is no ordinary stone. Not even an ordinary "precious" stone. It has a "certain
something" that made a Chinese emperor offer fifteen cities for a jade carving he
could hold in one hand; that made Montezuma smile when he heard that Cortes was
interested only in gold?? This is how begins one of the most beautiful books about
Jade: "Jade, Stone of Heaven" by Richard Gump. Jade name comes from the Spanish:
"Piedra de Ijada", that then passed in French as ?Le jade?, but it was known for
the Chinese as "Yu".
For hundreds of years the word "jade" was used to describe a typically green gemstone
of the alkaline pyroxene mineral group, however, in about 1863 gemologists were
able to distinguish two types of the mineral, one which if often referred to as
jadeite and the other as nephrite. Nephrite usually occurs as aggregates of amphibole
crystals (silicate of magnesium) it is fibrous, hard to fracture and soapy in appearance.
Jadeite is made up of interlocking microcrystalline pyroxene crystals (silicate
of aluminium), it is more readily broken but more brilliant while polished. Even
though this distinction has been made, the word "jade" is still used freely in the
market to refer to both jadeite and nephrite. So Jade is not one gemstone but two!
In China and many other Asian countries, jade is believed to bring the wearer good
luck and long life.
It is also a symbol of high rank and authority. Jade can be found as gemstones,
usually cut en cabochon, and as carvings for pendants, amulets, pipes, table utensils,
and figurines. Many scenes from Chinese folklore are carved on jade discs and include
symbols for fortune, fertility and longevity. More than 2000 years ago the Chinese
used nephrite, due to its incredible tough structure, to carve weapons such as daggers
and clubs. Jadeite is more recent, it was discovered by Chinese on the late between
the XIII and the XVIII century and was fist named ?Yunnan jade? as it was coming
from north Burma through Yunnan traders. Jade is classified in the trade as Imperial
Jade, Commercial Jade or Utility Jade. The highest quality of jadeite is called
Seven sub categories of Imperial Jade including the ?kingfisher jade? or ?fei-ts?ui?
combine high transparency with a rich saturated emerald-green color due to chromium.
Imperial quality Jade is so rare and loved than top quality pieces can be more expensive
than diamonds of equivalent weight? "Commercial Jade" has the hue of green or violet,
with stripes, specks or spots of other colors. It is translucent to near opaque.
The violet variety owns its color to vanadium and or chromium and is famous as "Lavender
jade". For "Utility Jade" only the texture is determinant. Here no green or violet
is visible. Utility Jade is usually used in carvings as statues or utensils. Fine,
smooth, clear texture is the sign of top grade utility Jade. In carvings the value
is placed heavily on the quality of the workmanship. Natural color untreated Jade
is known as "A-Jade" but Jade as all the highly valued gemstones have many imitations
and is also sometimes treated: Jade is commonly bleached and is then known as "B-Jade".
The color of "B-Jade" does not usually last very long and "B-Jade" is more brittle
as its structure is usually damaged by acids. Jade can also be impregnated with
paraffin to improve its luster, or heated to