GEMS, NATURAL AND ARTIFICIAL 



amethyst, being merely a quartz crystal and of far too 

 little value to merit attention from the manufacturer 

 of artificial gems. 



Gems of the true sapphire order are manufactured 

 by bringing alumina to a liquid state, by the agency of 

 extreme heat; the gems crystallize from the solution 

 on cooling. Fortunately it is not necessary, as in the 

 case of the diamond, to have the operation performed 

 under pressure; hence the relative facility with which 

 these gems may be produced. A practical difficulty is 

 found, however, in the fact that the crystals tend to 

 take the form of thin plates, unsuited to the purpose 

 of the gem-cutter. This is the chief reason why arti- 

 ficial rubies and emeralds have not long been familiar 

 in commerce, for it is almost seventy years since the 

 first true rubies were made in the laboratory. The ear- 

 liest successful experiments in this direction were made 

 by Gaudin in 1837, who produced true rubies of mi- 

 croscopic size. Ten years later Ebelmen produced the 

 white sapphire and the ruby-like spinel; but it was 

 not until 1877 that MM. Fremy and Feil succeeded in 

 making crystals of a size from which gems could be 

 cut; and still another quarter of a century elapsed 

 before a method of manufacture was devised that could 

 put the enterprise upon a commercial basis. 



The original experimenters, and numerous succeed- 

 ing ones, adopted the method of fusing alumina in the 

 presence of some substance, such as borax or barium 

 fluoride, that would act as a solvent. As the solvent 

 evaporated, the alumina crystals were deposited, 

 their color being predetermined partly by the quantity 



