173 



in which tlie synthetic stones are cut. They are cut abroad so cheaply 

 that tliey can be sold in America for less than the price per carat charged 

 for cuttinj; alone by the American lapidary. It is thus probably the in- 

 ferior surface finish of the synthetic stone that reveals itself to the 

 trained touch of the expert. I have carefully polished a specimen of 

 synthetic ruby to determine this point, and while I can feel a difference 

 between the synthetic stone of commerce and the natural stone, I am 

 unable to distiuiruisli any difference between my finely polished synthetic 

 stone and a natural one. 



I have shown that gem experts have decided that the boules of syn- 

 thetic corundum gems are single crystals and that they crystallize either 

 in the hexagonal or in tlu' tetragonal system. Professor Moses of Colum- 

 bia University said also that the parting figures suggested the hexagonal 

 system. The experts also said that the crystals were anhedral or face- 

 less. I wish now to add some evidence from my study of them that indi- 

 cates that the boules are not altogether faceless, and then to advance 

 evidence along two different lines to prove that the crystals arc of the 

 hexagonal system, as was indicated by the parting figures. 



Observation of a considerable number of the Ijonles shows that there 

 is a flattening on one side of nearly every boule, and an optical study 

 of the boules shows that this llattening is nearly parallel to the basal 

 planes of the crystal. Viewed with the dichroiscope perpendicularly to 

 the flattened place there is no dichroism. The dejith of color, too, is 

 greatest when viewed in this direction, and that would be true of natural 

 ruby when viewed perpendiculai-ly to the basal planes of the hexagonal 

 prism. On grinding the surface i;'arallol to the flattened place a slightly 

 pearly effect is seen, and this surface thus ja-oduced is more difficult to 

 polisli than a surface that cuts across the grain in any other direction, 

 ibis is generally Irue when working parallel to the cleavage of a natural 

 crystal, and thus indicates that the flattened place on the boule represents 

 the base of the prisnj. On this flattened face markings appear, indicating- 

 distortion of the edges of the layers of the material. There is a drawing 

 down and curving of the edges of the layers as they cross the basal plane 

 as though some force had distorted the layers as they arrived. These 

 markings go far down toward the stem of the boule, indicating that the 

 direction of crystallization is early determined. In a few boules the flat- 

 tening is absent, and then I have fonnd that the optical axis lies up 



