OPAL, 



"The Opal, when* pure and uncut in 

 its native rock," says Ruskin in his lec- 

 ture 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 admira- 

 tion 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 inter- 

 est in these colors may be heightened 

 by reading what Ruskin has further to 

 say of them : "We have thus in na- 

 ture, chiefly obtained by crystalline con- 

 ditions, 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 al- 

 ways 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 sud- 

 denly to have lost their hues never to 

 regain them, while others previously dull 

 and lusterless have become radiant as 

 the rainl)ow. 



Prof. Eglcston, of New York city, re- 

 lates that a bottle of cut Opals once 

 given him by a prominent jewelry firm 

 because they had lost their color, after 

 remaining in his ca1)inet for a time re- 

 gained tlicir l)rihiancy and retained it. 

 P>nl \n liav(> opals rc<;ain their color is, 



122 



unfortunately, far less usual than 

 for them to lose it. The gem often ex- 

 hibits brilliant colors when wet either 

 with water or oil that disappear when 

 it is dry. Taking advantage of this pe- 

 culiarity dishonest dealers often keep 

 opals immersed until just before offer- 

 ing them for sale. The experience of 

 having stones so treated as well as oth- 

 ers 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, how- 

 ever, trace the origin of the supersti- 

 tion to Sir Walter Scott's novel, "Anne 

 of Geierstein," in which the baleful in- 

 fluence 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 super- 

 stition 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 crystal- 

 lizes, 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 or- 

 ganic 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 ac- 

 count 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 

 rcas<in it is usual and desirable to allow | 



