IRON ORES OF THE GREAT VALLEY RANGE.
As before observed, this is the great region of the brown hematites, or the hydrated peroxides of iron. These ores were not formed in the manner of the Azoic magnetic and specular ores. They are never found in strata or intercalated with the limestones and slates in or on which they exist, but are invariably formed in bunches, "nests," or irregular masses, in the hollows and crevices of the limestones, or in the soft clays which border the outcrops of the lime against the sandstones and slates, both to the east and west of the valley.
The eastern side of the valley, or where the limestones, slates, and shales are strati fied on the Potsdam sandstone, is its most persistent bed; and here may be found a range of brown hematites which extend from the Chattahoochee in Alabama to the Lehigh in Pennsylvania, and how far beyond may be inferred from the extent of the formation. But between the points named the writer is familiar, and states the facts from practical sources. This range of ore is persistent, and may be found at any point within the distance named, but it is developed in far greater abundance at some points than others. Through Tennessee and Virginia it exists in an almost unbroken line, but made up of constantly changing deposits. Here we may find a thin, irregular stratum of ore imbedded in clay, there a mountain mass of moss-grown rocks of iron; here a mere string of ore, or simply red or ochry clay, and there a suc cession of "nests" distributed without strike or con formity.
On the higher grounds of Southwestern Virginia, in Pulaski, Wythe, and Smyth counties, this ore presents a partially stratified appearance, and exists in immense beds lying in the clays, which always accompany it, but never stratified between other rocks. We have never seen sandstones or slates over
lying it, except where the contractions of the accompanying rocks have forced them selves over it in inverted form.
On the northwest side of the valley this form of structure or deposit is not so promi nent, though the same character of nests, benches, and masses is found. The distri bution is not so general, and the amount of ore is much more limited. It is sometimes found as the oxidized outcrops of ferriferous slates, or in a stratum on or between thin bands of limestones, sandstones, and shales; but these deposits are limited and have but little depth.
In addition to those two general ranges of ore, we find deposits of this hematite scat tered promiscuously through the valley from edge to edge,—in some places assuming the shape of ridges and hills; in others we find it deposited in the hollows or crevices of the sometimes lying against the face of sandstone rocks which traverse the valley, and in so many other forms that it would be tedious to describe them.
These deposits are never deep. They are always found in bunches or shallow basins in the soft clays which fill the depressions of the limestones, and on or between the rocks without regard to conformability.
Though the Azoic belt contains an incalculable amount of iron ore, and mountain masses exist which would seem sufficient to supply the wants of the world for thousands of years, we hazard nothing in stating that more available ore exists in this parallel range, from Alabama to Lake Superior, than exists in that; and that the brown oxides of the limestones are more than equal in quantity and quality to the magnetic and specular ores of the gneiss.