172 



graphic uiul optical tests sliow tliat tlio material submitted is crystallized 

 and that the cone hy all tests is one homogeneous faceless (anhedrali 

 crystal. The crystalline, oiilical and <ttlier characteristics determined are 

 closely those of natural sapphire. In the absence of natural faces or 

 cleavages the crystallirie system, as determined by the optical tests, may 

 be either hexagonal or tetragonal. The parting figures point to the hexa- 

 gonal system. Any two natural substances which were as nearly identical 

 in chemical and crystallographic characters as the si>ecimeus submitted 

 and natural sapphires woidd be called identical. The difference is one 

 of origin " 



While expert mineralogists are agreed that these synthetic pnxhicts 

 are identical with the natural in all their i)roperties. yet the synthetic 

 stones may in nearly every case be distinguished from the natural l>y one 

 wlio is trained in seeking ndnute differences due to the difference in origin. 

 As is now well known in the trade, the synthetic stones frequently contain 

 bubbles which ai'e always round or rounding in lorni. Natural corundum 

 gems also frequently contain bubbles, but tlu'se are always bounded by 

 crystal planes and are hence angular in appearance. Lacking the bubbles 

 stritxi may be seen in tlie syntlietic stones, esp-ecially in the rubies, and 

 these strife, while parallel like those so often seen in natural stones, are, 

 unlike the latter, not straight but curving. The color, too. in the case of 

 the ruby, is not (luite e(iual to that of the best natural stones, although 

 in this respect I hojie to show that the defect is probably due to improinn' 

 cutting rather than to .-my r"al difference in the m.-iterial. The synthetic 

 rubies seem also to interfere with the passage of light through them to a 

 greater extent than the natural stones when the latter arc clear. This 

 results in a sort of general illumination of the interior of the stone. One 

 might say that the material was not optically a vacuum and that the 

 Tyndall effcu-t was produced. The Hashes ol' light ]>roduced by total re- 

 fiectioii from the rear facets of tbe stone ai-e therefore seen against a 

 backgi'ound of faintly illnminatcd mat'-ri.-il inste;id of against :i dark 

 backgroiUKl, as in the natui-al ruby. Tbi-; dctrai Is from the beaut.v of 

 the synthetic ruby somewjuit. and it is tins pliciioinrnon I lieli(>ve which 

 enables an e.xpei't to t<'l! by inspection wilboul the aid of a lens whether 

 u stone is a natural oi- .1 synthetic rub.v. Some experts have claimed that 

 they coulil tell by the touch alone whether a stone was a syntlu-tic or a 

 natural one. This dilference 1 bclie\c to be due lo the \erv liaslv manner 



