GEMS AND PRECIOUS STONES. 41
ZIRCON.
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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