IRON ROCK, 
93 
exposed to the weather, it has been cut into a variety of useful 
articles, as candlesticks, inkstands, &c. The form of the crys¬ 
tal can not he distinguished from pyroxene, but the faces being 
too dull to admit of the use of the reflecting geniometer, it may 
still differ from it in its dimensions. 
As a mineral, it was regarded by the late Prof. L. C. Beck 
as a mixed mineral, consisting of steatite and pyroxene. This 
view is apparently sustained by Beudant, who obtained from 
Sahla steatitic pyroxene swhich retained the form and cleavage 
of pyroxene. But contrary to this doctrine, it may he said 
that Ihe mineral is perfectly homogeneous, at least as much so 
as serpentine, limestone, or any other mineral or rock usually 
regarded as simple. No foreign matter can be detected by the 
microscope, either in the form of plates, amorphous or crystal¬ 
line grains. It is not uncommon to find hornblende and pyrox¬ 
ene combined in distinct crystalline particles, which together 
make up a crystal of the form of pyroxene. In this case the 
mixed nature of the mineral is evident to the senses, and it is 
as easy to refer each to the proper species, as it is the particles 
composing a mass of granite. I see no reason why we should 
assume a mineral to be mixed of two or more minerals in the 
absence of all external evidence. There is no objection, how¬ 
ever, to receiving this mass into our list of rocks, although it 
may be found hereafter to be confined to the northern part of 
New York. 
OCTAHEDRAL AND RHOMBOHEDRAL IRON ROCK. 
§ 67. The largest bodies of magnetic or octahedral iron ore 
known in this country are subordinate to the hypersthene rock 
in the Adirondack group of mountains in the western part of 
Essex county, New York. The iron rock has a jointed struc¬ 
ture, or it is traversed by divisional planes which bound large 
tabular masses. It is interlaminated w r ith masses of this rock, 
and in some instances seems to disappear beneath it. At 
Adirondack one of the bodies of iron ore is between 700 and 
800 feet thick. It disappears beneath the rock, and its actual 
