Page:Popular Science Monthly Volume 41.djvu/675

Rh mica from the East Indies has been quite heavy and has closed many of the American mines. The recent tariff of thirty-five per cent is leading to their partial reopening.

All these mines are more or less alike so far as their natural features are concerned. The chief differences are artificial, and consist in the methods of mining and handling the mica. The mines of western North Carolina have been largely exploited and may well serve as a type.

As one travels across the State to the westward, one passes over three distinct belts of country: the lowlands, covered by recent alluvial deposits; the middle or Piedmont section, a low plateau underlaid by older sandstones and shales; and, last of all, the western or mountain section, in which the Appalachian system reaches its finest development, and in Mount Mitchell its culminating point. The trend of the rocks, in this mountain section is pretty evenly northeast and southwest; they dip at angles which are generally forty-five degrees or over. There are a few mica mines to the east of the Blue Ridge, but the most of them and the best lie to the west. Once beyond this barrier, and evidences of mica abound on all sides. One sees the sunlight reflected from plates of mica on distant hill-sides, and the glitter of tiny scales in the bed of every brook. These look so much like gold that one is tempted to turn Argonaut, and try to bring again the golden fleece. For Colchis, it is easy to read Carolina. The talcose schists and slates of the eastern escarpment are here succeeded by the oldest crystalline rocks of the continent, belonging presumably to the Huronian or Laurentian period. There are giant upthrows of granite and gneiss, and these are full of fissures carrying the coarsely crystallized matrix in which the pay mica is found.

It must not be thought, however, that all these veins are alike profitable, or even that the same vein can be relied upon for any great distance, for that would be far from the experience of the practical mica-miner. It is indeed impossible, even after this lapse of time, when some of the mines have been worked intermittently for more than a quarter of a century, to reach any general conclusions as to what conditions are most favorable for a profitable mine. Old miners say that this or that indication is a sure sign of a good mine, but the shrewdest of them confess that mica-mining is pretty much like gambling. A certain amount is staked in the shape of labor and supplies, and one gets in return either hundreds of dollars' worth of mica, or perhaps only barren quartz and feldspar.

Many of the veins occur in a fine-grained black gneiss, which passes with the mountain miners under the name of "slate."

The vein generally dips with the bedding of the gneiss, but