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 found 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 connexion 
with a bed or vein.f 
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.^ 
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 relations 
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. 
+ Mr. Mather thinks, that in Putnam county, the magnetic iron ore occurs in true veins. 
t Dr. W. Horton’s Report on the Geology and Mineralogy of Orange County. New-York Geological Reports, 1839. 
