It
is supposed to have been the topaz of early writers, but its
identification has always been uncertain, and is so at the present
day. It is supposed to have been the chrysoberyl of Werner, and the
cymophane of Hauy, and has also been connected with the beryl and other
gems ; but at present the chrysolite, peridot, and olivine are
identical, only differing in colour.
The
Eomans considered this gem of greater importance than most other
precious stones, as they set it transparent, considering it to have
sufficient brilliancy unaided; most other gems they foiled with gold or
copper. They also used it for engraving. Two intagli are in existence,
one engraved with the head of Minerva, the other with that of Medusa.
The
chrysolite takes'a very fine polish, but it is stated to be difficult
of attainment. A copper wheel is used for the cutting, and the
polishing is done with Tripoli powder and oil. It is cut as a rose
diamond, or sometimes " step cut;" occasionally it is cut en cabochon. The gem is dichroic, giving squares, one of a green colour, the other straw-yellow.
The
chrysolite is essentially a volcanic mineral, commercial stones being
found in Egypt, Turkey, Africa, Australia, France, &c. ; in fact it
may be sought for in any volcanic region. Prom a scientific point of
view its presence in lavas and other igneous rocks, and the discovery
of olivine in meteorites, opens up a large field for consideration and
investigation. The chrysolite is commonly disseminated in basalt and
lavas in grains, although at times it is found as large as a turkey's
egg. Large, well-defined crystals are very uncommon.
There
are some good specimens of the peridot in the British Museum, and in
the Museum of Practical Geology, London. The best peridots obtained
during the middle ages retain their superiority at the present time, no
finer specimens having been discovered. The best peridots come from
Ceylon, Pegu, and Brazil. The word peridot in Oriental language
signifies a gem.
Transparent
bright-green chrysolites are fairly common in many of the auriferous
drifts of the Colony. It has been found in the Shoalhaven and Hunter
Rivers, also in some of the creeks that fall into the Cudgegong, county
Phillip ; at Bingera, the Barrier Bange, and at r> undle; in a trap
dyke on the tipper Murray, and in basalt at iDverell, and many other
places.
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