Page:The American Cyclopædia (1879) Volume IX.djvu/424

410 and in Oregon.—5. Franklinite. This is an ore analogous in composition to magnetite, but part of the iron is replaced by manganese and zinc. Its formula is (Fe, Mn, Zn)O, (Fe, Mn)₂O₂. It crystallizes in the isometric system; specific gravity about 5; hardness 5.5 to 6.5; streak dark reddish brown. It contains about 46 per cent. of iron, 17 of manganese, and 13.5 of zinc. It occurs at Franklin furnace and Stirling Hill, N. J. It is first treated to extract the zinc, and the residues are then smelted for spiegeleisen.—The reductibility of iron ores depends more on their molecular structure than their chemical composition. While the natural magnetites are classed with the more refractory ores, owing to their dense structure, the magnetic oxide resulting from the roasting of spathic ore is reduced with ease. The same contrast is noticed between the anhydrous and hydrous hematites.

—The distribution of the iron ores of the United States, with relation to the resources of the country in mineral fuel, has been well stated in the “Report on Iron and Steel” of Mr. Abram S. Hewitt, United States commissioner to the Paris exposition of 1867, as follows: “The position of the coal measures of the United States suggests the idea of a gigantic bowl filled with treasure, the outer rim of which skirts along the Atlantic to the gulf of Mexico, and thence returning by the plains which lie at the eastern base of the Rocky mountains, passes by the great lakes to the place of beginning, on the borders of Pennsylvania and New York. The rim of this basin is filled with exhaustless stores of iron ore of every variety, and of the best quality. In seeking the natural channels of water communication, whether on the north, east, south, or west, the coal must cut this metalliferous rim, and in turn the iron ores may be carried back to the coal, to be used in conjunction with the carboniferous ores, which are quite as abundant in the United States as they are in England, but hitherto have been left unwrought, in consequence of the cheaper rate of procuring the richer ores from the rim of the basin. Along the Atlantic slope, in the highland range from the borders of the Hudson river to the state of Georgia, a distance of 1,000 miles, is found the great magnetic range, traversing seven entire states in its length and course. Parallel with this, in the great limestone valley, which lies along the margin of the coal field, are the brown hematites, in such quantities at some points, especially in Virginia, Tennessee, and Alabama, as fairly to stagger the imagination. And finally, in the coal basin is a stratum of fossiliferous ore, beginning in a comparatively thin seam in the state of New York, and terminating in the state of Alabama, in a bed of 15 feet in thickness, over which the horseman may ride for more than 100 miles. Beneath this bed, but still above water level, are to be found the coal seams, exposed upon mountain sides, whose flanks are covered with magnificent timber,