12 MEMOIR ON EMERY. 



found, I will allude to the process of segregation which has 

 given rise to this formation. 



It would appear that the substances eliminated from the 

 calcareous rock were silica, alumina, and oxide of iron, and 

 that these three, in the exercise of homogeneous and chemical 

 attractions, have given rise to the minerals which constitute 

 and are associated with emery. In my collection there is a 

 specimen exhibiting this fact in a remarkable manner. It is 

 a nodule, showing emery in the center, with two concentric 

 layers, the inner of chloritoid and the outer of emerylite; the 

 latter was in contact with the limestone. 



Emery — Mixture of corundum (alumina a little hydrated) and oxide 

 of iron. . 



Chloritoid — Silica 24, alumina 40, oxide of iron 28, water 7. 

 Emerylite — Silica 30, alumina 50, lime 13, water 5. 



It is seen that in commencing from the external surface, in 

 which direction we must regard the consolidation of the nodule, 

 the larger portion of silica eliminated has combined with a large 

 portion of alumina and some lime to form a peculiar mineral; 

 next, the remainder of the silica combines with an additional 

 quantity of alumina and considerable oxide of iron to form 

 another mineral; and finally, the remaining alumina and oxide 

 of iron crystallize separately. Facts of this kind in geology 

 are not infrequent, but they are always highly interesting and 

 worthy of remark. 



In concluding the geological considerations of emery with 

 reference to the localities in Asia Minor and the neighboring 

 islands, I would remark that at some future time, when the 

 observations become extended, it will doubtless be found that 

 the emery forms the geognostic mark of extensive calcareous 

 formations in that part of the world, just as the flints do in 

 the chalk of Europe. 



MINERALOGICAL TOSITION OF EMERY. 



Emery is considered by some as corundum; others suppose 

 it represented by some rock or other, not always the same, in 

 which corundum is disseminated in greater or less quantity; 

 others again consider it a mixture of corundum and oxide 

 of iron. I am of opinion that the latter is the most correct 

 manner of regarding this substance. 



