. Economic Papers. tunnel to the northeast of it. The country rock is mica gneisswhich strikes about N. 75° E. and dips 55° S. The pegmatite is only approx-imately conformable with the gneiss, and so far as seen varies from 10 to 15feet in thickness. It contains numerous small horses or streaks of micagneiss or schist included parallel with its walls. The upper part of the mine has been worked at a number of places, andin such positions as to show an irregular pegmatite formation or severalmasses of pegmatite. The last operations had been in progress about oneyear at the time of visit and the
. Economic Papers. tunnel to the northeast of it. The country rock is mica gneisswhich strikes about N. 75° E. and dips 55° S. The pegmatite is only approx-imately conformable with the gneiss, and so far as seen varies from 10 to 15feet in thickness. It contains numerous small horses or streaks of micagneiss or schist included parallel with its walls. The upper part of the mine has been worked at a number of places, andin such positions as to show an irregular pegmatite formation or severalmasses of pegmatite. The last operations had been in progress about oneyear at the time of visit and the nature of the work is shown in figure 17, 70-foot tunnel was driven in a N. 75° E. direction on a mica vein. Fromthis an incline was run in a southwesterly direction on a dip of about 35°.The incline was about 70 feet long, 20 feet wide, and 10 feet high. A benchwas left on the northwest side in barren rock. The waste and mica werehoisted from the incline by means of a hand whim at the head of the Plan Cross section Figure 17.—A, Plan of Poll Hill mine, Yancey County, N. C. B, Cross section of pegmatite at end of incline at (a) in A. The wall rock is biotite gneiss, through which the pegmatite cuts andinto which it forks out. Figure 17, B, represents the vertical cross sectionof the pegmatite exposed in the face at the bottom of the incline. The posi-tion of the bench in barren gneiss is shown on the side. The incline wasdriven on the pegmatite where that rock was diverted from its course acrossthe gneiss into lens-shaped masses. These lenses became smaller or pinchedout in a short distance on each side. The quality of the mica from the Poll Hill mine is good and the colora clear rum. Aley Mine.—The Aley mine is at the head of Browns Creek about 3miles southwest of Micaville. It has been opened by at least three tunnels,one an incline, and by open cuts and a shaft 40 feet deep. The last workwas that of the J. E. Burleson Company in 1904. The vein strikes N
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