MEMOIR ON EMERY. 



25 



this memoir is blue, except that of Kulah and of Adula, which 

 is of a greenish -gray. All that I have to add to what is already 

 known of this mineral relates to its composition and effective 

 hardness; the latter was ascertained in the way already de- 

 scribed in speaking of the emery, and it has been found to vary 

 with the composition of the mineral. The analyses were made 

 in the same manner as those of the emery, and the results which 

 I have obtained are as follows : 



Localities. 



Sapphire of India 



Kuby of India 



Corundum of Asia Minor 



Corundum of Island of Nicaria 



Corundum of Asia 



Corundum of India 



Corundum of Asia 



Corundum of India 



Corundum. 



EC hr; 

 - p >"b 



I » 



100 

 90 

 77 

 65 

 60 

 58 

 57 

 55 



4.06 



3.88 



Composition. 



1.60 

 3.9210.68 

 3.601.66 



3.89 

 3.80 

 3.91 



2.86 

 3.74 

 3.10 



97.51 

 97.32 

 92.39 

 87.52 

 86.62 

 93.12 

 87.32 

 84.56 



- o-. 



3 a 



C 



1.89 

 1.09 

 1.67 

 7.50 

 8.21 

 0.91 

 3.12 

 7.06 



1.12 

 0.82 

 0.70 

 1.02 

 1.00 

 1.20 



0.80 

 1.21 

 2.05 

 2.01 

 3.85 

 0.96 

 2.61 

 4.00 



trace. 



0.25 



The most remarkable fact ascertained by these analyses 

 is the presence of water in variable quantity in all varieties 

 of the corundum except the sapphire and ruby. To me this 

 fact has a certain value in proving that the corundum and 

 the sapphire are formed under different circumstances and do 

 not belong to the same geological formation. The different 

 structure of these two species of corundum might make one 

 suspect a difference in the condition of their formation; and 

 this is somewhat confirmed by the results of the beautiful 

 experiments of M. Ebelmen in making artificial corundum by 

 subjecting alumina and borax to the heat of a porcelain fur- 

 nace for many hours — circumstances under which he always 

 obtained crystals under some of the modifications of hyaline 

 corundum, and never as prismatic corundum. In addition to 

 this I remark that in my most thorough examination of the 

 localities of emery not the slightest trace of sapphire or ruby 

 was found. 



The quantity of water found to exist in corundum coming 

 from different localities is variable, and it would appear that, 

 all other things being equal, those containing the least water 



