MAGNETIC OXIDE OF IRON. 
9 
O'Niel Mine. This is about a quarter of a mile northeast of the preceding, and is a vast bed 
of the magnetic oxide of iron. The ore is generally hard and compact, but is often traversed 
by seams which are studded with crystals having the form of the regular octahedron, which 
is occasionally modified, and rarely passes into the form of the cube. (See Fig. 1, 2, 3 and 5.) 
This mine has been extensively worked. The ore contains iron pyrites, and requires to be 
roasted before it is used by the smelter; but it yields a good iron of the red short variety. 
Its immediate associates are white calcareous spar, which is abundant, rose coloured garnet, 
green coccolite, dark coloured pyroxene and massive hornblende ; amianthus in delicate fibres, 
serpentine, and probably arragonite also occur. 
The O’Niel ore is strongly attracted by the magnet, and possesses polarity. The following 
is its composition: 
Protoxide and peroxide of iron,. 95.75 
Silica and alumina,... 4.25 
The Clove or Wilks Mine, which is the most westerly of the great iron ore deposits now 
wrought, is situated about a mile south of the village of Monroe. The ore is strongly attracted 
by the magnet, and is sometimes granular and pure, at others it is largely mixed with iron 
pyrites. It makes red or hot short iron, and generally requires roasting before it is used. At 
the south end of the mine, which has been opened about 500 feet, the ore occurs in the form 
of a black powder, which is here called fine or soft ore, and is probably the result of the 
decomposition of iron pyrites. Large quantities of this variety have been obtained, and it 
does not require the ordinary roasting process. 
According to Dr. Horton, the solid ores of this mine are in layers having the direction and 
dip of the rock in which they occur. The layers are from a few inches to a yard or more in 
thickness. The immediate associates of the ore are mica, hornblende, quartz, feldspar, asbes- 
tus, occasionally carbonate of lime, a kind of serpentine or soapstone, and perhaps, though 
rarely, chrome-iron ore in minute octahedrons. 
The following are the constituents of one of the purest specimens of the Clove ore, by my 
analysis: 
Protoxide and peroxide of iron,. 98.90 
Silica and alumina,.. 1.10 
But the granular magnetic ore is usually mixed with iron pyrites, as above stated. 
It may be added, that masses of well characterized hematite are found on the surface, in 
the immediate vicinity of this mine. 
The remaining deposits of the magnetic oxide in this county are much less important than 
those previously described. They are principally in the town of Cornwall. 
A bed of the magnetic oxide of iron occurs about one or two hundred yards east of the 
reservoir at West-Point. Its quantity is not known, but it has been traced, at short intervals 4 
for some distance in a southerly direction towards Meek's Mine, on the western part of Bear 
hill, southwest of Buttermilk falls. The ore of the latter mine is said to be titaniferous.* 
Part I. 
2 
Mather. New-York Geological Reports, 1839. 
