80 JOURNAL OF THE 



oidal granites, and the extreme dislocation of all the members 

 of the series, would seem to indicate an age beyond the Silurian. 

 It would require patient and long continued observation, based 

 chiefly on strati graphical and petographical relations, to settle 

 this obscure problem. It is known, however, that the mica- 

 bearing rocks of the plateau between the Blue Ridge and the 

 Smoky Mountains do not cross the Smoky Mountains, except 

 sporadically, and then only for a short distance. On the western 

 side of the Smoky Mountains, in Tennessee, we meet with the 

 Silurian, but as it does not here carry mica, though ouly a few 

 miles from the North Carolina mica zone, the assumption that 

 the "mica zone" occurs in rocks older than the Silurian is some- 

 what strengthened, be that age Huron ian or Laurentian. 



Assuming, therefore, for the present that the mica occurs in 

 the very oldest rocks, we may inquire as to its immediate con- 

 geners. 



A mica vein is only a vein of very coarse granite, in which 

 the feldspar, quartz and mica have crystallized on a large scale. 

 It differs from ordinary granite chiefly in this respect, that while 

 in granite the crystallizing forces have, in a measure, interfered 

 with each other in a mica vein, each has had, so to speak, free 

 play. The difference between the two can best be conceived by 

 imagining the ingredients of granite magnified several hundred, 

 iudeed, several thousand, times. The crystals of mica in granite 

 seldom attain a greater size than one-sixteenth or one-fourth inch 

 across; a single mica "block" from Mitchell county made two 

 two-horse wagon loads and could not have weighed less than 

 2,000 pounds! A single block of "A" mica from the Mart 

 Wiseman mine in Mitchell county was (> feet long and 3 feet 

 wide. The crystals of feldspar in granite are seldom larger than 

 one-sixteenth or one-fourth inch across. A single feldspar crys- 

 tal from the Balsam Gap mica mine, Buncombe county, weighs 

 800 pounds, and is now in the State Museum at Raleigh. A 

 piece of a feldspar crystal, now in the possession of the writer, 

 obtained from the Deake mica mine, Mitchell county, weighs 30 

 pounds. It originally weighed 500 pounds, but was uufortu- 



