L. P. Venen.
OPAL.
“The Opal, when pure and uncut in its native rock,” says Ruskin in his lecture on Color, “presents the most lovely colors that can be seen in the world except those of clouds.”
While not all of us may share the great art critic’s preference for uncut stones, there are few probably who will not join him heartily in his admiration of the brilliant gem from whose depths come welling up tints of so varied hue that we appropriately speak of them as colors at play. Our interest in these colors may be heightened by reading what Ruskin has further to say of them: “We have thus in nature, chiefly obtained by crystalline conditions, a series of groups of entirely delicious hues; and it is one of the best signs that the bodily system is in a healthy state when we can see these clearly in their most delicate tints and enjoy them fully and simply with the kind of enjoyment that children have in eating sweet things. I shall place a piece of rock opal on the table in your working room; and if on fine days you will sometimes dip it in water, take it into sunshine and examine it with a lens of moderate power, you may always test your progress in sensibility to color by the degree of pleasure it gives you.”
The Opal is indeed one of the most fascinating of gems; yet often elusive and at times disappointing. Of its freaks and foibles strange stories are told. Gems of brilliant quality are known suddenly to have lost their hues never to regain them, while others previously dull and lusterless have become radiant as the rainbow.
Prof. Egleston, of New York city, relates that a bottle of cut Opals once given him by a prominent jewelry firm because they had lost their color, after remaining in his cabinet for a time regained their brilliancy and retained it. But to have opals regain their color is, unfortunately, far less usual than for them to lose it. The gem often exhibits brilliant colors when wet either with water or oil that disappear when it is dry. Taking advantage of this peculiarity dishonest dealers often keep opals immersed until just before offering them for sale. The experience of having stones so treated as well as others which might with more reason be expected to retain their brilliancy, lose it, has very likely led to the superstition commonly attached to the Opal that it is an unlucky gem. Some authorities, however, trace the origin of the superstition to Sir Walter Scott’s novel, “Anne of Geierstein,” in which the baleful influence of the Opal plays a prominent part, and it is stated that within a year of the publication of the book the price of Opals declined fifty per cent in the European market. Even if the superstition did not originate in either of these ways it was probably from a source quite as trivial and it should prevent no one from enjoying the pleasure to be derived from the beauties of this gem.
Chemically, Opal is oxide of silicon with varying amounts of water, the water varying from 3 to 9 per cent. It is, therefore, closely allied to quartz, but differs physically in being softer and not as heavy. Further, it never crystallizes, and it is soluble in caustic potash, which quartz is not. It is infusible, but cracks and becomes opaque before the blowpipe. In sulphuric acid it turns black, on account probably of the organic matter it contains.
Its hardness is sometimes as low as 5.5 in the scale in which quartz is 7 and its specific gravity is from 1.9 to 2.3, while that of quartz is 2.6. On account of its relative softness a cut Opal often does not retain its polish well and requires frequent smoothing. Opals when first taken from the ground are often softer even than the above and for this reason it is usual and desirable to allow them to harden or “season,” as it is called, for some time after quarrying, before they are polished.
OPAL.
LOANED BY FOOTE MINERAL CO.