masses, or of globular shape, and pale tints, from brown to
pearl gray, though not unfrequently they exhibit rich prismatic
colors. They are softer than the Hungarian variety, but compare favorably with it for brilliancy and durability. It has been
reported that one of the richest opal-mines in the world has,
within a few years, been opened in the province of Queretaro,
Mexico, yielding numerous fine specimens with a great
diversity of colors, including blue, pink, red, green, yellow,
cream color, and black. The fire-opal, the most resplendent
of all the different kinds of this wonderful gem, is found in the
greatest perfection in porphyry, at Zimapan. It is translucent
and emits brilliant fiery-red, yellow, and green reflections ; but
it is easily impaired by exposure to moisture and changes in
temperature.
Remarkable specimens are known to occur in different collections. There is one in the imperial cabinet of Vienna,
found at Czernowitz, near the Pruth, in 1770, which weighs
seventeen ounces, and, not withstanding its cracks and fissures,
the sum of fifty thousand dollars has been offered for it, but
the government refused to sell it, even at that price. The
finest Hungarian opals are seen among the crown jewels of
Austria, though France numbers among her state collections
two very valuable gems of this kind. Probably the most
remarkable opal on record was the one owned by the Empress
Josephine, which was called the " Burning of Troy," on account
of the innumerable red flames it emitted, as if on fire. The
under side was perfectly opaque, but the upper portion, being
transparent, served the purpose of a window through which
were seen the glowing rays of fiery light, very appropriately
compared to the conflagration of a great city.
Magnificent examples of the opal have been frequently
exhibited among the curiosities of modern expositions. A
