tour 21 of 21
Chinese jade
Jade: the material
The English term 'jade' is used
to translate the Chinese word
yu, which in fact refers
to a number of minerals including nephrite, jadeite, serpentine and
bowenite, while jade refers only to nephrite and jadeite.
Chemically nephrite is a calcium magnesium silicate and is white in
colour. However, the presence of copper, chromium and iron gives
colours ranging from subtle grey-greens to brilliant yellows and
reds. Jadeite, which was very rarely used in China before the
eighteenth century, is a silicate of sodium and magnesium and comes
in a wider variety of colours than
nephrite.
Nephrite is found
within metamorphic rocks in mountains. As the rocks weather, the
boulders of nephrite break off and are washed down to the foot of
the mountain, from where they are retrieved. From the Han period
(206 BC - AD 220) jade was obtained from the oasis region of Khotan
on the Silk Route. The oasis lies about 5000 miles from the areas
where jade was first worked in the Hongshan (in Inner Mongolia) and
the Liangzhu cultures (near Shanghai) about 3000 years before. It
is likely that sources were known that were much nearer to those
centres in the early periods and were subsequently
exhausted.