175 



As further evidence of this structure I fiud that in the case of a 

 cabochon cut (smooth, convex upper surface) rubj^ which I myself cut 

 from a fragment of a iioule, I can plainly see a six-pointed star when 

 viewed in direct sunlight or even when seen by the light of a single candle. 

 This star effect is due to tlie presence in the material of microscopic bub- 

 bles, which produce somewhat the same effect as is produced by dust 



flexure IR ^^^ubu 

 Vi e<ije.di oo I^Lat aide • 



I)articles in a beam of light crossing a darkened room. The six-pointed 

 character of the star plainly indicates that the material has the hexagonal 

 arrangement, as a tetragonal crystal under sinylar conditions would )iro- 

 duce a cross rather than a six-pointed star. 



