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The Opal.
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from
Hungary nearly as large as a man's fist, and weighing 17 ozs. Perhaps
the finest Opal of modern times was that of the Empress Josephine,
which was called the " Burning of Troy," from the numberless red flames
blazing on its surface.
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AUSTRALIAN OPALS.
Of
late years Precious Opals of singular beauty have been brought in
quantities from Australia. Attention was first directed to their
occurrence in Queensland by Mr. H. W. Bond, who found them near
Cooper's Creek, which runs into the Barcoo River. Since then several
other localities in Queensland have been found to yield Opal ;
some of the most important deposits being at Fermoy, or Sandy Creek,
situated 125 miles west of Longreach, and 90 miles from Winton.
The
Queensland Opal occurs in veins and pipes in sandstone, and especially
in brown ferruginous nodules. By probing the soft sandy rock, the hard
ironstone concretions are detected ; and on breaking them open, the
Opal is seen as an incrustation on the walls of the cracks. The opaline
layer is usually but thin, and advantage is sometimes taken of these
layers to cut cameos of Opal on an ironstone matrix.
A
few years ago, Mr. G. J. Hooley, in tracking a wounded kangaroo, in a
remote part of New South Wales, found Opal, and this discovery led to
the opening up of the White Cliffs' field. This locality is situated on
the River Darling, about 50 miles from Wilcannia. The Opal occurs in
Sandstone of Upper Cretaceous age, corresponding to the Desert
Sandstone of Queensland ; it occupies vertical and horizontal fissures
in the rock, yet the actual matrix of the Opal is not sandstone, but a
whitish substance described variously as kaolin and as marl-stone. It is
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