ORES OF THE COAL MEASURES.
The ores of our coal-fields are numerous and widely distributed; but, unfortunately, their beds are generally thin and their yield is low. But, though not as rich as the mine-ores of South Staffordshire, England, they will compare favorably with the ores of the Welsh coal-fields, which are so extensively used in the blast-furnaces of Wales.
The table of analysis which we take the liberty of copying from Rogers's State Survey shows the average yield of the anthracite ores to be equal to the yield of the Welsh ores ; while the yield of the ores of the bituminous measures is in excess.
In the anthracite regions these beds of ore do not present favorable positions for mining with economy: they are generally enclosed in heavy walls of hard rock, and are generally too thin to mine without removing the accompanying top or bottom strata. In a few cases they exist above coal-seams and in such close proximity as to admit of one being mined with the other; but this is the exception and not the rule.
While the red-ash measures contain more of the ferruginous rocks, and we find iron diffused more generally through their measures, among the white-ash beds of coal are found the most consistent beds of ore,—that is, the ores of iron exist in peculiar strata rather than diffused through the mass. We frequently find small beds of ore in the vicinity of the conglomerate; but these are thin, irregular, and lean. The first important ore-bed which we find in the anthracite regions is above B, or the Buck Mountain coal-bed, and in the vicinity of C. This undoubtedly produces the ores which we find so frequently cropping out behind the Mammoth throughout the anthracite regions ; and not only the anthracite, but we find it also consistent throughout the Great Alleghany coal-field.
It is developed at the Barclay and Blossburg mines, and used extensively at Johns town, in the Cambria Iron Works, and is found and used extensively in Armstrong, Venango, Clarion, Mercer, Butler, Beaver, and Allegheny counties; while on the Great Kanawha, in West Virginia, it is found on its consistent horizon over the ferriferous limestone.
This bed of ore varies in the anthracite regions from twelve inches to thirty inches in thickness, and yields from 20 to 40 per cent. of iron. It is, however, extremely silicious
in the anthracite measures, but contains a small percentage of lime and manganese. This ore is a protocarbonate wherever found, always containing more or less carbonate of lime, and sometimes a small amount of the carbonates of magnesia and manganese. 3n the bituminous regions it is sometimes a calcareous ore, containing so large an amount of lime as to become a ferruginous limestone. The outcrops of this bed are always oxidized, and present either a red or brown hematite, in which case it is very rich and productive.
In the vicinity of the Mammoth we find several small seams of ore ; but they are not of a size or character ever to render them available for the production of iron to any extent.
The second bed of importance is in the vicinity of the Primrose, G. This is a black band, and may be the same as that which is developed in the Bear Valley basin, though we are not familiar with the locality of this black band in that basin. We know, how ever, that the Primrose bed does not extend far in that direction.
There are numerous small beds of ore among the red-ash coal-seams, frequently in close proximity to the coal, and always above it. Most of these ores may be mined with economy; but their silicious character will .prevent their use in the blast-furnace, unless prepared, as before stated, by burning, crushing, and washing.
This process is not expensive, and the ore resulting can be reduced with a comparatively small amount of flux and a cor responding proportion of coal.
The accompanying figure, 174, represents the combination of coal and iron as found generally in the English and Welsh coal-fields. The connection of coal and iron is also found in the same proximity in the anthracite red-ash beds, but the proportional amount of ore is much less, while the coal is generally much greater.
In some portions of the Richmond (Virginia) coal-field, par ticularly in the Deep Run basins, a carbonate of iron overlies the principal seam, as represented above, but the ore is less and the coal greater in pro portion, as in the case of the anthracite red-ash seams.