169 



Notes on the System of Crystallization and Proper Cutting of 

 THE Synthetic Corundum Gems. 



r.Y Fkaxk r>. Wadk. 



It is with some hesitation tliat I am attemi)tin.!j; ti> present hefore the 

 Physi'-ai Science Section of the Indiana Academy of Science a i>aper 

 upon so technical a subject as tlie system of crystallization of the syn- 

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

 tion of one whose serious worlv 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 in cutting synthetic 

 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 this 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 ])arallel to tiie basal 

 j)lanes of the hexagonal prism. 



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

 of an amorphous mass — it is in reality crystalline, in fact a single crystal. 

 Hence in cutting it proper regard should be had for its oi>tical 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 the direction of the optical axes. 



r> was in the endeavor to work out methods of determining these 

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

 literature that was available upon the suliject 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 

 paper. 



The earlier workers attempted to obtain rubies by the fusion of 

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

 drogeu l>lowi)ipe. M. <Taudin, in 1837. using the oxyhydrogen blowpipe 



