MAGNETIC OXIDE OF IRON. 3 



veins in the primary rocks, especially in granite, gneiss and mica slate. It has also been met 

 with in serpentine, greenstone and hornblendic rocks, and is said to have even been observed 

 in what have been called transition and secondary strata. 



In northern New- York, magnetic iron ore is almost as widely diffused as are the mountains 

 of granite and of gneiss, in the counties of Warren, Essex, Clinton and Franklin. The rocks 

 in which this ore is fotmd in these counties, however, differ somewhat in their characters. In 

 some parts of Essex, they are chiefly composed of quartz and hornblende of a fine granular 

 structure, while in others they are granite or sienite made up almost entirely of dark coloured 

 feldspar, containing masses of labradorite, and in some places a small proportion of pyroxene. 

 In Clinton county, the rock in which this ore is found is a granite composed of quartz and 

 feldspar, quartz and hornblende, or feldspar and hornblende, sometimes with scales and seams 

 of mica forming gneiss. In the county of Franklin, the rocks which accompany the magnetic 

 iron are said to contain much more hornblende, which is frequently observed in crystalline 

 masses in the walls of the beds and among the ore.* 



The magnetic iron ore in these counties is, with scarcely an exception, in what are usually 

 termed beds, or deposits of variable widths and unknown depths running parallel to the course 

 of the stratification, when the rock is stratified. The general direction of these beds is north- 

 northeast and south-southwest ; but when subject to local variations, the course is north and 

 south, or northeast and southwest. Sometimes, however, this ore occurs in large masses in 

 the rock, without any regular parallelism of the sides, as is the case in Essex county. And 

 lastly, it is occasionally disseminated in particles in the rock, apparently without any coimexion 

 with a bed or vein.t 



In Orange county, where the magnetic oxide of iron is very abundant, it is always found 

 in the granitic gneiss or gneissoid granite so common in the highlands. It lies in beds and 

 layers in this rock, and has the same line of bearing and dip. Where it exists in layers, they 

 are from one inch to twenty feet in thickness, and in some places the layers of the ore alternate 

 several times with those of the rock. But the ore sometimes occurs in masses, the magnitude 

 of which has never been ascertained. J 



The same general description will apply to the geological situation of the magnetic oxide 

 of iron, as found in the counties of Putnam, Saratoga, Washington, Herkimer and Lewis. 

 And from a review of all the observations which have been made on this subject, there is little 

 doubt that the position and geological relations of this important mineral are entirely similar 

 in all parts of the State in which it has been found. 



Geographical range. From what has just been said in regard to the geological relation* 

 of the magnetic iron ore in this State, a tolerably correct idea may be formed of its geogra- 

 phical distribution. 



 See the Reports of Dr. Emmons and Mr. Hall. New-York Geological Reports, 1837. 



t Mr. Mather thinks, that in Putnam county, the magnetic iron ore occurs in true veins. 



X Dr. W. Horton's Report on the Geology and Mineralogy of Orange County. New-York Geological Reports, 1839. 



