MEMOIR ON EMERY. 21 



in the manner detailed when this fact became known, so that 

 I have but these two cases to report. It will simplify the 

 analysis of corundum if pulverization in a diamond mortar be 

 found sufficient, and I propose examining specially into this 

 question. 



The water which was found in the emery comes from the 

 corundum, a fact which will be shown when the analysis of 

 pure corundum is given, which will be in the second part of 

 the memoir. A very minute quantity of what has been esti- 

 mated as water might be a little oxygen lost by the oligist 

 which is sometimes found in emery. Those emeries which 

 contain the least water, every thing else alike, are the hardest, 

 as instanced by that from Kulah, notwithstanding the quantity 

 of iron it contains. The silica existing in emery is most often 

 in combination with alumina or the oxide of iron, or with both. 

 For this reason we must not always regard the quantity of 

 alumina as an indication of the quantity of corundum in the 

 emery. 



ANALOGIES. 



Emery at first sight may be confounded with several ores 

 of iron, as magnetic iron, certain varieties of oligist, and some- 

 times with chromate of iron ; but the fracture of emery is stony, 

 which differs from these ores of iron, and besides the surface 

 exposed is of a lighter color. From the numerous observations 

 made I may set it down as a general rule that any blackish or 

 dark-blue rock of a strong argillaceous smell, that scratches 

 agate well, with a specific gravity in the neighborhood of 4, is 

 sure to be emery. 



THE MINING OF EMERY. 



The mining of this substance is of the simplest character. 

 The natural decomposition of the rock in which it occurs facili- 

 tates its extraction. As has already been mentioned, the rock 

 decomposes into an earth in which the emery is found imbed- 

 ded. The quantity found under these favorable circumstances 

 is so great that it is rarely necessary to explore the rock. The 

 earth in the neighborhood of the blocks of emery is almost 

 always of a red color, and serves as an indication to those who 

 are in search of the mineral. Sometimes, before beginning to 



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