MAGNETIC OXIDE OF IRON. 
5 
many individuals. This, however, is no fault of the chemist; for the specimens sent to him 
for his experiments, instead of being the average of the produce of the mine, are almost 
always the purest and best which have been obtained. In all these cases, perhaps the true 
value of a chemical analysis consists in the determining the kind of ore, and the nature of the 
foreign matters mixed with it; but the proportion of these matters in large quantities of the 
ore, and indeed the true economical value of the ore can only be learned by a careful inspec¬ 
tion of the locality. And it is this consideration which renders it important that, in the study 
of minerals with reference to their uses in the arts, the trials of the laboratory should be united 
with the observations of the geologist. 
The purity and consequent value of the magnetic iron ores may in general be very easily 
determined in those cases where the questions in regard to their quantity, and the ease of 
conducting mining operations, have been previously settled. For this purpose, it is only 
necessary to take a known quantity (say an ounce) previously reduced to powder, and then to 
subject it to the continued action of a strong magnet. The pure magnetic oxide will thus be 
separated from the foreign matters with which it was mixed ; and from its weight, the propor¬ 
tion which it bears to the whole may be at once ascertained. This, it will be observed, is the 
principle of the separating machine, which is so advantageously employed in many parts of 
Northern New-York. 
I shall now proceed to describe in detail the more important localities of the magnetic 
oxide of iron, commencing at the southern part of the State, and passing from thence towards 
the north. 
Rockland County. Specimens of magnetic oxide of iron, sometimes possessing polarity, 
are not unfrequent in the granitic ranges of this county. I have a specimen from the vicinity 
of Ramapo, which has a specific gravity of 5.019 ; but this ore has no where been found in 
beds or veins of any considerable extent. 
Orange County. This county contains very abundant and rich localities of the magnetic 
oxide of iron. It is doubtful, indeed, whether the quantity which exists here does not exceed 
that found in an equal area in any part of the world. The towns of Monroe, Warwick and 
Cornwall, are the most remarkable in this respect. 
Stirling Mine , or Stirling Mountain. This is a vast deposit of iron ore which occurs in a 
mountain of moderate elevation, rising at the south end of Stirling pond in the town of Monroe. 
From the excavations which have been made in various parts, there can be no doubt that this 
deposit of ore is three miles in length. The mine is said to cover a surface of more than 
thirty acres, by survey. Over a part of this area the ore is bare, while in others it is covered 
by soil and rock of from six inches to five feet in thickness. 
The ore from this mine is usually granular, but it occasionally occurs in octahedral crystals, 
and is associated with ilmenite, crystallized green hornblende, pyroxene, green mica, quartz 
and flesh-coloured feldspar. It is feebly magnetic, and is also sometimes mixed with iron 
Pyrites, to which perhaps the peculiar character of the metal obtained from this ore is to be 
ascribed ; being, according to Mr. Townsend, intermediate between cold and hot short. 
