MAGNETIC OXIDE OF IRON. 5 



many individuals. This, however, is no fault of the chemist ; for the specunens sent to him 

 for iiis 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 analy.sis 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 miited 

 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 tiieir quantity, and the case 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. Tlic 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 gi-anitic 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 jjond in the town of Monroe. 

 From the excavations which have been made in various parts, there can be no doubt tliat this 

 deposit of ore is three miles in length. Tlie mine is said to cover a surface of more than 

 thirty acres, by survey. Over a part of this area tlie 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. 



