10 MEMOIR ON EMERY. 



although in every instance I have found it associated with the 

 old limestone overlying mica-slate, gneiss, etc. 



It is imbedded either in the earth that covers the limestone 

 or in the rock itself, and exists in masses from the size of a pea 

 to that of several tons' weight, generally angular, sometimes 

 rounded, and when in the latter form they do not appear to 

 have become so by attrition. 



The masses in the soil possess but little interest for 'the 

 geologist, as they may have been left there by the decomposi- 

 tion of the rock or been transported from other positions; still 

 the latter is difficult of supposition in reference to what is 

 found at Gumuch-dagh, for here it is only on the summit and 

 not on the sides of the mountain that the emery has been 

 traced. But having had the means of studying the emery and 

 rock in contact, I have come to the firm conclusion that the 

 emery has been formed and consolidated in the limestone in which 

 it is found, and that it has not been detached from older rocks, 

 as granite, gneiss, etc., and lodged in the limestone at the period 

 of its formation. My reasons for so thinking are the following : 



1. In no instance could the closest investigation of the older 

 rocks of these localities that are below the limestone furnish 

 the slightest indication of the existence of emery there; and 

 moreover the masses of emery in the limestone never had 

 fragments of another rock attached to them. A few thin 

 layers of mica-slate were found in the limestone, but they 

 were not in contact with the emery nor contained any traces 

 of corundum. I dwell thus much on this point because in my 

 specimens the calcareous rock in connection with the emery is 

 under two forms — that of the original rock, and that formed by 

 the infiltration of calcareous water in the fissures which exist 

 near the surface. 



2. The limestone immediately in contact with the emery 

 differs almost invariably in color and composition from the 

 mass of the rock, and at Kulah, where the marble forming the 

 rock is remarkably pure (as evinced by analysis), the part in 

 contact with the emery is of a dark-yellow color, resembling 

 spathic iron, and contains a large portion of alumina and oxide 

 of iron. The thickness of this interposing coat between the 

 emery and the marble is variable; but what is certain, it passes 

 gradually into white marble, so that their crystalline structures 



