dimensions
to be fashioned into fair-sized bowls six inches or more in diameter.
Jadeite, especially the emerald green variety, is however, more
generally employed for smaller objects, such as snuff-bottles,
bracelets, carved plaques, inlays, rings and beads. It belongs to the
pyroxene group of minerals and is therefore nearly related to diopside
and to spodumene.
The
chief distinctive characters of jade and jadeite may be summarized in
the following tabular statement where the chemical composition of
typical specimens of each species is presented in percentages : —
For
further details concerning the archaeology and artistic use of jade and
jadeite reference should be made to Dr. Bushell's Handbook of Chinese
Art, vol. i, pp. 134-150. In Mr. Spencer's translation of Dr. Max
Bauer's " Precious Stones," pp. 458-470, will be found a full account
of the occurrence, composition and properties of these two minerals.
Pyrites.
There
are two minerals having the same two elements in the same proportions
as constituents, but differing in physical and chemical characters.
These two minerals are pyrite or iron pyrites,an d marcasite. Both
contain iron and sulphur, 46.7 per cent, of iron, and 53.3 per cent,
sulphur, corresponding to 1 atom of iron and 2 atoms of sulphur. The properties of the two minerals may be compared thus :
