superseded by the more abundant mines in New South Wales.
Why
the opal displays so many brilliant colors has been somewhat of a
riddle to scientists. The most probable theory of the varied coloring
is that it is formed by strata in the stone, containing different
percentages of water which break up the ray of light similarly as a
prism does. The most beautiful and fascinating opals are the dark ones,
known as black opals. These come from Australia, and since they are in great demand today, command large prices.
In
history the opal has always been famous and was very highly prized by
the Romans. In contradiction to the superstitions that are now
associated with the gem by some people the opal was then regarded as
having the virtues of all the stones whose colors it displayed. It was
supposed to cheer the despondent and was in general a symbol of hope.
And like the turquoise, it was believed to change color if its wearer
grew ill and regain it when he recovered.
