138 CORUNDUM, TTS OCCURRENCE AND DISTRIBUTION. 
would not interfere at all in the manufactnre of a vitrified wheel. 
Some of the ore that has been mined here carries a very high per- 
centage of garnet. 
The analyses that have been made of this ore all shoAv a high per- 
centage of alumina, which was to be expected, as the spinel is an 
alumina mineral, (MgFe)C),Alo03, and contains about 50 per cent of 
this oxide. An error is very often made in judging the percentage of 
corundum in an ore by calculating as corundum the total percentage 
of alumiuji obtained in a chemical analysis, which would represent, 
however, the alumina contained in all the aluminous mineral compo- 
nents of the ore. (See p. 21.) 
Some of the ore at these mines is inidoubtedly a true emery, but a 
considerable portion of it is a mixture of spinel and magnetite, which 
Avhile not a true emery, will make a useful abrasive. This whole or 
body might be called a spinel -emery. 
From wdiat has been said regarding the occurrence of the emery 
in these Peekskill deposits, their pockety nature is what would be 
naturally expected, and this has been characteristic of all the mining 
that has been done in this district. ^ 
The Blue Corundum Mining Company, of Boston, Mass., is one of 
the largest miners in this section. It has leased the emery deposits on 
the land of Isaac McCoy, 3 miles southeast of Peekskill. Its prin- 
cipal work is on the summit of a hill about half a mile south of the 
McCoy house and consists of an open cut 40 to 50 feet deep, 40 feet 
long, and 12 to 20 feet Avide. The emery ore is from 4 to (') feet wide, 
but it is broken up by bands of serpentine and chloritic rocks. In 
some of the ore the corundiun is very distinct, occurring in elongated 
bluish-white crystals u]) to 5 nun. long. This ore is very free from 
garnet. 
Another deposit of emery has been encountered 50 feet below the 
summit, and still another 25 feet farther down. No mining has been 
done at either of these points. 
The ore is hauled by teams to Peekskill, where it is shipped by rail 
to Easton, Pa. 
On a hill 1 mile east of the McCoy mine H. M. Quinn, of Phila- 
delphia, Pa., has mined on the land of John H. Buckby. Pockets of 
emery were encountered on the summit of the hill and at a number of 
points on its western slope, but they soon pinched out. About 50 
feet below the summit a face of rock 15 to 20 feet high and 40 feet 
across has been exposed. The only emery seen here is the remnant of 
a pocket. 
As far as could be learned the emery deposits of the Tanite Com- 
pany, of Stroudsburg, Pa., are also leased. They are on the lands of 
Henry Heady, Oscar Dalton, and David Chase, and are for the most 
part similar to the deposits just mentioned. The ore on the land of 
