1886.] NEW YORK ACADEMY OF SCIENCES. 7 



made by one exact process or at one time. Their dull appear- 

 ance is evidently Ine in part to the bubbles. The optical prop- 

 erties of these stones are such that they are evidently individual 

 or parts of individual crystals, and not agglomerations of crys- 

 tals or groups fused by heating. 



In my opinion, these artificial rubies were produced by a pro- 

 cess similar to that described by Fremy and Feil {Com2Jtes Rendus, 

 1877, p. 1029), by fusing an aluminate of lead in connection 

 with silica in a siliceous crucible, the silica uniting with the lead 

 to form a lead glass, and liberating the alumina, which crystal- 

 lizes out in the form of corundum in hexagonal plates, with a 

 specific gravity of 4.0 to 4.1, and the hardness and color of the 

 natural ruby, the latter being produced by the addition of some 

 chromium salt. By this method rubies were formed that, like 

 the true gem, were decolorized temporarily by heating. 



It is not probable that these stones were formed by Gaudin's 

 method [Comptes Rendus, xix. , p. 1342), by exposing amorphous 

 alumina to the flame of the oxyhydrogen blowpipe, and thus 



•^CV.'t. 





Fig. 4. — Acicular crystals in sapphire Fig. 5. — Cuneiform crystals in ruby and 



(enlarged 100 diameters). sapphire (enlarged 200 diameters). 



fusing it to a limpid fluid, which, when cooled, had the hardness 

 of corundum, but only the specific gravity 3.45, much below that 

 of these stones. Nor is it at all likely that they were produced 

 by fusing a large number of natural rubies or corundum of 

 small size, because by this process the specific gravity is lowered 

 to that of Gaudin's product. The same also holds good of 

 quartz, beryl, etc. 



The French syndicate referred the matter to M. Friedel, of the 

 Ecole des Mines, Paris, sujiplying him with samples of the stones 

 for examination. He reported the presence of the round and 

 pear-shaped bubbles, and determined the hardness and specific 

 gravity to be about the same as in the true ruby. On analysis, 

 he found them to consist of alumina, with a trace of chromium 

 for the coloring matter. The cleavage was not in all cases dis- 

 tinct, and the rough pieces given to him as examples of the gem 

 in its native state had all been worked, so that nothing could 

 be learned of their crystalline structure. When properly cut 

 according to axes, they showed the annular rings. The extinc- 



