GEMS AND PRECIOUS STONES. 41
Crystalline System—Tetragonal.
Hardness—7.5.
Specific gravity—4'7—4*8.
Lustre—Adamantine.
Cleavage—Parallel to faces of the prism, indistinct in most instances.
Composition—Silicate of zirconia, Zr02 Si03. Silica, 33 ; zirconia, 67 per cent.
There are several varieties of thia gem known by special names, as "hyacinth," which is red and transparent. " Jargoons," or "jargons," are colourless or smoky-tinted zircons, (those were so named in allusion to the fact that while resembling the diamond in lustre they were, in comparison with that gem, almost worthless). The zircon or zirconite is grey or brown, and in some specimens almost opaque. The name is from the Arabic, zirk, meaning a precious stone. Besides these well-defined varieties, the diversity of colour in this gem is very great, ranging from red to brown, from yellow to orange, and from blue to green.
This stone forms a very fine gem, and when of a ruby colour might be mistaken for the spinel ruby, although the higher specific gravity of the zircon would at once decide the question. When the coloured stones are heated, they become quite colourless in most instances, thus differing from either the spinel or the garnet. They do not fuse in the flame of the blowpipe, which is a characteristic difference from the garnet. The crystalline form at once determines the zircon from those stones resembling it in some of its characters.
The perfectly transparent stones have a lustre almost approaching that of the diamond, and to this may be attributed the indifference with which these gem-stones are now treated. They have been used for the purpose of fraud, having been set in massive gold rings, pawned as brilliants, and of course never redeemed. A file will not touch them, so that this test for " paste " fails in this case. The high dispersive power which the zircon has, also assists to render the determination, by general appearances, deceptive, but the test of hardness would at once decide the matter, as the zircon is scratched by topaz, and this is only 8 in the scale.
"Were it not for its deceptive characters, its natural properties place it, for ornamental purposes, next to the diamond. There is a variety obtained at Matura, Ceylon, which is known as the " Matura diamond". It is often sold in the bazaars of India for the genuine diamond.
Some of the red specimens are remarkable for the vividness of their tints, which have been likened to flames of fire ; but with all these good characteristics to recommend them, these gems are not favourites, and fashion counts for a great deal.
Of course, like all gems, it has been endowed with supernatural properties, especially during the middle ages. It was considered to have the power to bring sleep, riches, honor, and wisdom ; to drive away the plague, and to protect the wearer from evil spirits. We look back with amusement at the superstitious reverence given to these precious stones in those times, but to-day the superstition in reference to some gems still remains, although, perhaps, in a lesser degree. That some precious stones have the power to bring ill-luck, and that their possession brings disaster and ruin, is firmly believed by many. One of the minor industries of Australia Buffers at the present time from the effect of this lingering superstition.
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