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THE OPAL. 251
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The Opal is displayed to best advantage when cut en cabochon, or with a convex surface.
Pliny
tells that the rich Roman Senator Nonius was proscribed by Mark Antony
for the sake of a magnificent Opal which he possessed, (valued at two
millions of sesterces, or sixteen thousand, and eight hundred pounds) ;
a stone as large as a hazel nut, but which he refused to sell.
The
so-called Black Opals consist of the matrix (penetrated in all
directions by veins, and spots,) of Opal forming a mixture known
sometimes as " Soot of Opal." But certain stones sold as Black Opal
have manifestly been modified in colour by staining, or by heat. The
American Opal is generally less fiery, and less milky in appearance
than the Hungarian Stone.
Of
late years some very brilliant opals have been sent into the market
from Queensland. The Harlequin, and Noble Opals have the same chemical
composition, i.e., ninety per cent of silica, and ten per cent of water.
Next
in value ranks the Fire Opal, or Girasol, with bright hyacinthine,
yellow, or fire-red reflections. Again, there is the rare dark Opal,
black, with a sullen red-hot glow in its inner heart, which would put
the burning Carbuncle to shame. Likewise the " Prime d'Opal," or Opal
Seeds, with points brilliantly coloured, set in a sober matrix, and
beautiful exceedingly when in large masses.
Other
minor kinds are the deep brown ferruginous Opal, the waxen Green, and
the Jaspery ; also the Garnet-red, the rich Topaz-yellow, and the
violet blue ; all these being forms and phases of that grand crystal of
common flint, the "Precious," or "Noble" Opal, the " Child of love."
This " Precious," or " Noble," Opal
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