THE PIEDMONT COAL-FIELD.
This small deposit of coal lies west of the Richmond coal-field, as located on the map representing it in connection with the Richmond coal-field. It exists in the counties of Prince Edward and Cumberland. The formation extends from a point near the James River across the Appomattox at Farmville, and in all probability extends in connection with the Dan River coal-field. But the coal has only been developed in workable seams near Farmville, or in the vicinity of the Piedmont mines, as located on the map. The area of coal is small, and probably does not extend over 20 square miles in the vicinity of Farmville. The undulate excessively; the basins are irregular, and the dips to all points of the compass. The bottom rock, resting on gneiss, is a coarse quartzose sandstone, of considerable thickness in the centre of the basins, but quite thin on its edges, where it crops out between the coal and the gneiss. We think this field the creation of a period following the Carboniferous, and earlier than the Richmond period, but formed in much the same manner and from the same materials. The field, however, has been much more disturbed by the subsequent action of the volcanic forces than the Rich mond. Numerous dikes and outbursts of trap rend the measures and divide the basins; and only a small portion of the coal is workable, in consequence.
The seams in this field are very thin, and would not be considered workable in the anthracite regions of Pennsylvania. They range from 6 inches to 30 inches. Of those above 12 inches there are 7 which have
been proved, in about 300 feet of measures, and lying, perhaps, 300 to 500 feet above the gneiss. The seams which have been proved in the vicinity of the gneiss, at the eastern edge of the coal-field, are very irregular and impure, frequently changing to impure anthracite in localities; while the coal generally is a dry bituminous, containing much sulphur and impurity, coking with difficulty, but producing a hard coke under a strong heat in the coking-ovens. Nothing but white, brittle cast iron can be produced with this coke in the cupola.
The coal is generally hard and difficult to mine; the seams not only thin, but frequently interrupted by "slip dikes," "upthrows," "down throws," and rock faults, as detailed in Chapter XIV.
This field has been developed within the last ten years, and only one operation or mine has been worked for local consumption, which, though conducted on a small scale, was the most systematic in Virginia or the South, having complete arrangements for pumping and hoisting: yet, owing to the smallness of the seams, the cost of mining was not less than $2.50 per ton delivered at the top of the mine.
The locality of this small coal-field, in the midst of a thickly-settled inland district, remote from other available coal, will make it valuable for domestic purposes only. In the vicinity of the Pennsylvania anthracites or the Alleghany fields, it would not be considered at present workable.