PRECIO US STONUS. 265 



is composed only of carbon. The second comprises all jewels the base of 

 whose composition is alumina. The list of these is much more varied than 

 might be supposed, since it contains stones as varied in apjDearance and 

 color as the sapphire, the ruby, the Balas ruby, the Spinel ruby, the topaz, 

 the emerald, the beryl, the aquamarine, the cymophane and the turquoise. 

 Alumina is the base of the common red and yellow clay which is found 

 everywhere in the utmost abundance, and the only mark of distinction 

 known to chemists between the common clay and the sapphire, or the em- 

 erald, is the fact that the latter are crystalized, and contain traces of me- 

 talic oxides which give color to the stones. The name corundum is ap- 

 plied by mineralogists to all varieties of crystalized alumina, whatever 

 their color. Colorless corundum is so brilliant as sometimes to be mis- 

 taken for a diamond, but it may be readily distinguished by its double re- 

 fraction, and by its small specific gravity. The corundums are often ex- 

 ceedingly valuable, rubies of perfect luster and purity being of greater 

 value than diamonds. The ruby ranks first for price and beauty among all 

 colored stones. It is of the pure red of the spectrum, and next after the 

 sapphire is the hardest of precious stones, always excepting the diamond. 

 Charles Achard, the highest authority in France in all that concerns the 

 traffic in colored stones, remarks that weight has not the same effect in 

 their case as in that of the diamond. Every diamond, from the very small- 

 est specimen upward has its value, like gold and silver, according to 

 weight; but in the case of rubies and otlier gems, the little specimens have 

 hardly any value, and these stones only begin to be appreciated at the mo- 

 ment when their weight withdraws them from the common lot, and assures 

 at once their rarity and high price. When a perfect ruby of five carats 

 enters the market, a price will be offered for it double the price of a per- 

 fect diamond of the same weight; and if a ruby reaches the weight of ten 

 carats, it will bring triple the j)rice of a diamond of the same weight (from 

 three to four thousand dollars). The carbuncle of the ancients is the same 

 as our modern ruby. The most fantastic qualities were formerly ascribed 

 to these wonderful stones. The carbuncle served to furnish light to cer- 

 tain great serpents or dragons when old age had enfeebled their eyes ; they 

 constantly carried these magical stones between their teeth, only dropping 

 them when it was necessary to eat and drink. According to St. Epiphanius, 

 the carbuncle has not only the property of shining brilliantly in darkness, 

 but its light is of a nature so extraordinary that nothing can arrest it, so 

 that it shines, for instance, through vestments with undiminished fire. 



Stones composed in whole or in jjart of silica are much more numerous, 

 and much less valuable than the aluminous stones. Quartz, transparent 

 and colorless, is the purest specimen of silica that can be obtained ; and 

 though when colored by the mixture of other ingredients it receives a 

 variety of names, it is no more changed in nature than would be the pieces 

 of the same silk which had received each a different color from dyeing. 

 "-Crystals do not ordinarily attain large dimensions. For the greater 



