48 GEMS AND PRECIOUS STONES.
During
the prevalence of a plague at Venice, at a time when the opal was much
worn, the attendants at the hospitals declared that before the death of
the victim the opal upon his finger would brighten and glow. It is not
difficult to understand the rapid spread a statement of this character
would make at such a time, and no scientific explanation would be
sufficient to remove the impression that this fatal gem foretold the
death of its owner, even if it did not prevent his recovery. It is well
known that the precious opal is very sensitive to the influence of
heat, and a jeweller will hold in his hand for a short time a specimen
he is about to show a customer; the heat from his hand being sufficient
to improve the appearance of the gem. Even the increase of temperature
of a warm day is sufficient to make a marked improvement in the opal.
It
is to be hoped, however, that the ill repute of the opal will go the
way of all superstitions, and the day is uot far distant when this gem
will again take its proper place among precious stones. Her Majesty the
Queen of England has done much to break down this prejudice, the opal
being a favourite stone with her ; and many members of the royal houses
in Europe, and also of the aristocracy, are now becoming purchasers of
the opal. Already (1895) opals are becoming fashionable in Europe.
The
principal supply of precious opal, before its discovery in Australia,
came from Hungary, where it is found in a claystone porphyry, in a
mountain range near Czernowitz. It is also found in the province of
Gracias, Honduras, and although less fiery than the Hungarian
specimens, the conditions of occurrence of the American opal, are
similar to those of its European rival. A specimen from Honduras,
weighing 602 carats, and valued at £5,000, was exhibited at the
Centennial Exhibition at Philadelphia in 1870.
The
Hungarian mines were discovered in the fifteenth century, and although
from that time a very large quantity of opal has been taken from the
mines (which are skilfully worked), they still produce fine specimens.
Two very large opals were found there in 1863, and exhibited at the
Paris Exhibition in 1867 ; one weighed 183 carats, the other 100
carats; the latter is said to be the finest gem of its class ever seen.
The
Queensland opals occur principally in the Gregory South District, in
the south-western portion of the Colony, being found in the M"Gregor,
Colemau, Grey, and Canaway Ranges, where it occurs in ferruginous
siliceous ironstone nodules, or in a "bandstone" underlying the
sandstone. The opal-bearing rock is obtained where possible by removing
the overlying sandstone. "When the amount of material to be removed
becomes too great, "driving" is resorted to, in the clay or cement
"bottom" underlying the opal-bearing bandstone. A collection of
photographs, showing this opal country, and the modes of working to
obtain the opal in this part of Queensland, is exhibited in the
Museum. I had the pleasure of inspecting a large consignment of these
opials which had arrived from Queensland. There were some hundred
weights of matrix and opal, presenting a very beautiful appearance.
Some of the specimens were large, and from which good gems could be
cut, but a very large quantity consisted of thin veins in the brown
ferruginous matrix, these being only fit for cameos, for which they are
particularly suited, the brilliant colours of the gem forming a marked
contrast to the dark background of the matrix.
During
the last few years beautiful opal has been found in this Colony, at a
locality known as White Cliffs. This field is situated in the county of
Yungnulgra, on the Momba Run, about 60 miles in a north-westerly
direction from Wilcannia. In the year 1889, a hunter found a piece of
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