THE NONMKTALLIC MINIi:RALS. 289 



of nearly a thousaiul pounds weight, and I have known a single V:)lock of miea to 

 make two full two-horse wagon-loads, and sheets of mica are sometimes obtained 

 that measure three and four feet in diameter. 



There are many peculiarities about these veins. Among the most important, in a 

 practical sense, is the arrangement of the different constituents of the vein inter .sy. 

 Sometimes the mica, for example, will be found hugging the hanging-wall; some- 

 times it is found against both walls; again it may be distril)uted pretty equally 

 through the whole mass of the vein; sometimes, again, it will be found collected in 

 the middle of the vein; in other cases, where the vein varies in thickness along 

 its course, the mica will be found in bunches in the ampullations, or bellies, of the 

 vein; in still other cases, where the vein has many vertical embranchments, the 

 mica will be found accumulated in nests along the upper faces of these processes or 

 offshoots. Those features of structure will be best understood from a few repre- 

 sentative diagrams. 



Figure 9 is a liorizontal section, with several transverse vertical sections, of a typ- 

 ical vein in Yancey County, at the Presnel Mine. The length of the section, i. e., 

 of the portion of the vein that has been stripped, is 125 feet; the thickness varies from 

 3 to 10 feet, except at a few points, as b c where it is nearly 20 feet. 



The crystals of mica are found in this mine generally near the foot wall, in the 

 recesses or pouches; at c, however, as seen in section D, it is found next the hanging- 

 wall. 



The inclosing rock in this case is a hard, gray slaty to schistose gneiss. * * * 



The feldspar, which constitutes the larger part of the mass of these veins, is often 

 found converted into beds of the finest kaolin; and, curiously enough, this was one 

 of the first and most valuable exports to England in the early part of the seventeenth 

 century, "packed" by the Indians out of the Unaka (Smoky) Mountains, and sold 

 under the name "unakeh" (white). This kaolin, like the mica, will doubtless soon 

 come again into demand, after lying forgotten for generations. 



Characteristic samples of the micas of the region are shown in 

 Specimens Nos. 18205, 18207, 62962, and 62964, U.S.N.M. 



In Alabama, along a line stretching from Chilton County, north- 

 east, through Coosa, Clay, and Cleburne counties, there are numer- 

 ous evidences of prehistoric mica mining. Many pits are met with 

 around which pieces of mica are still to be seen. In some places, just 

 as in Mitchell County, North Carolina, large pine trees have grown 

 up on the debris, so that a considerable time must have elapsed since 

 the mines were worked. About ten years ago. Col. James George, of 

 Clanton, Chilton County, prospected for mica, and some fairly good 

 specimens were obtained, but the investigations were not continued. 

 It is not thought that any mica has been marketed from Alabama. 

 The indications of good mica along the line mentioned aie, however, 

 sufficient to warrant additional and more extended examinations. Lit- 

 tle mica is reported from other Southern States, though some mines 

 have been opened in South Carolina, Georgia (Specimens Nos. 63139 to 

 63141, U.S.N.M.), Virginia, and West Virginia. In 1881, a mica mine 

 was opened in Anderson County, South Carolina, and some miners from 

 Mitchell County, North Carolina, employed. The enterprise was not 

 successful, and the miners returned home shortly afterwards. Good 

 mica has been found in South Carolina, notably in Anderson, Oconee, 

 and Pickens counties. The mica-bearing rocks of western North Caro- 

 NAT MUS 99 19 



