THE TECHNOLOGIST. [AuausT 1, 1864. 



40 WHAT PRECIOUS 'STONES ARE MADE OF. 



small air-bubbles in the strass may be readily detected with a good 

 magnifying glass, and the breath remains much longer upon it on 

 account of its bad conducting power, than upon real gems. 



The electrical power of jewels is also another test, for it is stated 

 that genuine stones retain their electricity from six to thirty hours, 

 whereas the false stones retain it scarcely as many minutes. The ap- 

 pearance of some " California diamonds " will deceive many persons, 

 for they have a lustre and evanescent fire which is extremely beautiful. 

 This is soon lost, however, by wearing ; perspiration, moisture, and 

 dirt, washing the hands, &c, soon destroy the appearance of this paste, 

 and in a few days it becomes as dull and lack-lustreless as the eyes of 

 a dead fish* 



The diamond is the ultimate effort, the idealization, the spiritual 

 evolution of coai — the butterfly escaped from its antenatal tomb, the 

 realization of the coal's highest being. Then the ruby, the flaming red 

 oriental ruby, side by side with the sapphire and the oriental topaz — 

 both rubies of different colours — what are they ? Crystals of our argil- 

 laceous earth, the earth which makes our potter's clay, our pipe clay, 

 and common roofing slate— mere bits of alumina. Yet these are among 

 our best gems, the idealizations of common potter's clay. In every 100 

 grains of beautiful blue sapphire, 92 are pure alumina, with one grain 

 of iron to make that glorious blue light within. The ruby is coloured 

 with chromic acid. The amethyst is only silica, or flint. In 100 grains 

 of amethyst 98 are simple pure flint — the same substance as that which 

 made the old flint in the tinder-box, used before our phosphorus and 

 sulphur-headed matches, and which, ground up and prepared, makes 

 now the vehicle of artist's colours. Of this same silica are also corne- 

 lian, cat's-eye, rock crystal, Egyptian jasper, and opal. In 100 grains 

 of opal 90 are pure silica, and 10 water. It is the water, then, which 

 gives the gem that peculiar changeable and iridescent colouring which 

 is so beautiful, and which renders the opal the moonlight* queen of the 

 kingly diamond. The garnet, the Brazilian — not the oriental — topaz, 

 the occidental emerald, which is of the same species as the beryl, all 

 these are compounds of silica and alumina. But the beryl and emerald 

 are not composed exclusively of silica and alumina ; they contain 

 another earth called glucina — from glukos, sweet, because its salts are 

 sweet to the taste. The hyacinth gem is composed of the earth, not so 

 long discovered, called zirconia — first discovered in that species of 

 hyacinth stone known as zircon. The zircon is found in Scotland. To 

 every 100 parts of hyacinth 70 are pure zirconia. A chrysolite is a 

 portion of pure silicate of magnesia. Without carbonate of copper 

 there would be no malachite in Russia or at the Burra Burra mines ; 

 without carbonate of lime there would be no Carrara marble ; the 

 turquoise is nothing but a phosphate of alumina coloured blue by 



° ' Scientific American.' 



