MEMOIR ON EMERY. 13 



Emery, properly speaking, is not a simple mineral, but a 

 mechanical mixture of granular corundum and oxide of iron, 

 in which the former usually predominates. It has not the 

 aspect of corundum disseminated in a rock, for it is found in 

 distinct masses of different dimensions and of great hardness, 

 and when broken giving way in the directions of fissures, 

 which exist commonly in the mass. Most frequently there is 

 no other evidence of the presence of corundum in emery but 

 its hardness. The oxide of iron present is always under the 

 form of magnetic oxide more or less mixed with oligiste; 

 sometimes it is titaniferous. There are other minerals asso- 

 ciated with the emery, all of which will be described hereafter. 



The aspect of this substance differs more than is supposed, 

 for until lately the emery brought from Naxos has been the 

 criterion by which to judge others. The localities that I have 

 discovered furnish me with specimens showing considerable 

 difference not only as regards color, but also in the structure. 



The Naxos emery is of a dark-gray with a mottled surface, 

 and with small points of a micaceous mineral disseminated 

 in the mass. It frequently contains bluish specks or streaks, 

 which are easily recognized as being pure corundum. 



The Gumuch-dagh emery is commonly of a fine grain, and 

 dark-blue bordering on black, not unlike certain varieties of 

 magnetic iron -ores. With this variety we frequently find pieces 

 of corundum of some size. The interior of the mass is toler- 

 ably free from the micaceous specks found in that of Naxos. 



The Kulah emery is usually coarse-grained, and much darker 

 than that of Gumuch-dagh, its external surface resembling 

 sometimes that of chromate of iron. 



The Nicaria emery in many instances presents a schistose or 

 lamellated structure to a very remarkable degree, so much so 

 that certain specimens might pass for gneiss. The color is 

 dark-blue and somewhat mottled, like that of Naxos. There 

 is also much that is quite compact found in the same locality. 

 The lamellated variety contains an abundance of a micaceous 

 mineral, which in this instance appears to have determined its 

 structure. 



The Samos emery, as yet found only in small quantities, and 

 in the form of nodules, is uniformly of a dark-blue color, some- 

 times of a coarse-grained and at other times of a fine-grained 



