Opals: Composition and Superstitions

Composition

"The opal, when pure and uncut in its native rock, presents the most lovely colors seen in the world, except those of clouds," says Ruskin, in his lecture on "Color." The mineral composing the opal does not, however, always show the brilliancy of colors which we usually associate with the gem. Chemically, it is an oxide of silica, and is therefore much similar to quartz. As a mineral, opal is quite common, and one of its interesting occurrences is in the Yellowstone Park, where the geyser and hot spring formations are composed almost entirely of this silicate known here as geyserite. It may be said, therefore, that the waters of the park build up cones of opal and fall into opal basins. In the rarer form in which it displays its many fascinating colors the gem is of comparatively rare occurrence. The most noted and most ancient mines are those of Czernowitza, in northern Hungary. It is well established that the Romans obtained their opals from these mines. At the present day, however, this ancient source has become superseded by the more abundant mines in New South Wales.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.

Superstitions