ORES OF THE AZOIC BELT IN VIRGINIA.
The Azoic mountain-region of North Carolina extends into Virginia, but its peculiar basin-shaped formations have only a limited area in this State, embracing only the counties of Floyd, Carroll, and Grayson.
The magnetic range, however, may be traced into Virginia by developments in Franklin and Bedford counties, and its continuation may be noted at intervals to the east of the Blue Ridge through a great portion of Virginia. But, though we have ex plored this State very extensively, and have shafted at many points on the peculiar magnetic range under discussion, we have never found it in great abundance. The veins or beds are thin, irregular, and much injured by impure matter. In the vicinity of the Peaks of Otter, large quantities of this ore lie scattered on the surface, but we have never been able to trace it to any body, nor have we ever heard of any large masses of magnetic ore being found on this range, or in the region where we would naturally expect to find the largest or most valuable beds of magnetic ores. The trap pean rocks, however, which abound in this region are generally impregnated with iron; and the whole Piedmont country, from the Blue Ridge to the Eastern granite ranges, is full of scattered iron ores, impregnating the rocks, coloring the soil, and existing in limited beds of oxidized surface ore, as red and brown hematites and black and red oxides.
In the vicinity of the saccharoid or crystalline limestones, as in North Carolina, there are numerous beds or bunches of brown oxides, but they are of limited extent, and have but little depth. Traced down, they almost invariably terminate in sparry, quartzose slates, or iron pyrites.
Parallel with the gold belts, which appear to be two in number, we find the eastern and western magnetic ranges. The saccharoid limestone and the accompanying oxides of iron exist between these ranges; while the formations containing the magnetic ore( appear to be older than the gold to the east, and newer or later than the gold to the west. But the reappearance of the granitoid gneissic in the Peaks of Otter and other
elevations of the Blue Ridge offers conclusive evidence of the repetition of the eastern ranges to the west, and, consequently, the magnetic ores which lie below the gold in the east are of the same ages and formation with those that lie geologically below the gold in the western range, or in the formations bordering on the eastern spurs of the Blue Ridge.
The Azoic belt in Virginia is wide, undulating, and made up of often-repeated axes, folded in sharp and frequently perpendicular strata. The formations are frequently cut by trappean dikes, and the debris of volcanic rocks are found throughout the eastern portion of the gneissic formations. All these rocks contain iron in limited quan tities. They appear to exist in their primitive condition, and, though denuded by subsequent floods, were never subject to the disintegrating process, which alone could precipitate their iron. Consequently, we frequently find large masses of black oxides in the eastern magnetic range scattered over the surface, but no beds in situ have yet been discovered. We have proved several of the reported magnetic beds of Eastern Virginia, but they all terminated in ferriferous trappean rocks at no great depth, or in impregnated quartzose slates. It is hard to account for the absence of this ore in Vir ginia in workable beds, since the Azoic belt is very extensive, and trappean rocks or volcanic outbursts are frequent. We can only account for it in assuming that this portion of Virginia was not covered by water at the period of those volcanic eruptions which produced our great Azoic ore beds, since it is evident that their occurrence was long subsequent to the formation of the gneiss in which they exist.
The great region of iron ores in Virginia is in the limestones of the Valley, and between the Blue Ridge and the North Mountains, to which we shall refer in that con nection.