169 



Notes on the System of Crystallization and Proper Cutting op 

 THE Synthetic Corundum Gems. 



By Frank B. Wade. 



It is witli some hesitation tliat I am attempting to present before the 

 Physii-al Science Section of tlie Indiana Academy of Science a paper 

 npon so technical a subject as the system of crystallization of the syn- 

 thetic corundum gems, when my study of them has been but the recrea- 

 tion of one whose serious work lies in another direction. 



It was while attempting to learn how to produce the best possible 

 results in the way of richness and depth of color iu cutting sjiithetic 

 ruby that I made a study of the crystalline form of the rough ruby 

 boules. The best lapidaries, in cutting natural ruby, long ago learned 

 that, to produce the deepest and richest color it was necessary to lay 

 the table of the cut stone parallel with the basal planes of the natural 

 hexagonal crystal. Fortunately tills method of cutting usually gave also 

 the largest possible cut stone from the rough material, as the natural ruby 

 has a tabular habit, with the greatest diameters parallel to the basal 

 planes of the hexagonal prism. 



Now — although the rough boule of synthetic ruby has the appearance 

 of an amori)lious mass — it is in reality crystalline, in fact a single crystal. 

 Hence in cutting it proper regard sliould be had for its optical properties 

 if the best results are to be obtained. The Boules, however, although sin- 

 gle crystals, have no well defined crystal faces or cleavages to reveal the 

 system of crystallization or tlie direction of the optical axes. 



It was in the endeavor to work out metliods of determining these 

 matters that I lyegan a study of tlie rough boules. I first looked up the 

 literature that was available upon the subject of artificial corundum 

 gems, and for the sake of refreshing your memory along this line I will 

 briefly review that part of it which leads toward the subject of this 

 pai)er. 



The earlier Avorkers attem]>ted to obtain rubies by the fusion of 

 alumina, either in glass or porcelain furnaces or by means of the oxyhy- 

 drogen blowpipe. M. Gaudin, in 1837, using the oxyhydrogen blowpipe 



