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:
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Jade. Jadeite.
Silica 58·0 58·0
Alumina 1·3 24·5
Ferrous oxide 2·0 1·0
Magnesia 24·2 1·5
Lime 13·2 2·3
Soda 1·3 12·7
Hardness 6° 7°
Specific gravity 2·98 3·33
For further details concerning the archæology 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, and 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:
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Pyrite. Marcasite.
Hardness 6·5 6·0
Specific gravity 5·2 4·8
Crystalline form Isometric Orthorhombic.
Colour Brass yellow. Pale or grey yellow.