Jackson.] 



88 



Specific gravities of specimens of the emery. 



Two specimens from South Mountain . 4.02 and 4.37 



Two specimens from North Mountain . 3.75 " 3.80 



Two specimens from Naxos, Greece . . 3.71 " 3.72 



The hardness of the emery, since it scratches topaz, is of course 9 

 of Mohs' scale. 



Chemical analysis of the emery of the North Mountain. 



Alumina 46.50 



Protoxide of iron 44.00 



Titanic acid 5.00 



Sihca and moisture 4.50 



100.00 



Specimens from the South Mountain. 



Alumina 45.50 



Protoxide of iron 43.00 



Silica, Titanic acid and water . • • . 11.50 



100.00 



The mineral was rendered soluble by successive fusions with bi-sul- 

 phate of potash, and lastly by fusion with a mixture of carbonate of 

 soda and hydrate of potassa. In other respects the analyses were 

 made in the usual way. 



After digesting the finely crushed and levigated emery with a mix- 

 ture of nitric and chlorhydric acids, so as to remove all the oxide of 

 iron that was free and soluble, we have for the composition of three 

 samples of emery. 



100.00 100.00 100.00 



From which it would appear that protoxide of iron is an essential 

 chemical ingredient in emery, and not an accidental admixture. 

 Dr. J. Lawrence Smith's experiments lead to the same result, but he 

 considers the oxide of iron to be an irregular mixture with the alum- 

 ina, and not a regular chemical constituent. In either case I think 

 emery ought to rank as a separate species and not as a granular 

 variety of corundum, from which it so differs In physical characters. 



