88 JOURNAL OF THE 



long-continued observations, conducted in a methodical and 

 scientific manner, preclude t he formation of definite and reliable 

 opinions. There are so many accessory circumstances that in- 

 fluence the quality of the mica — such, for instance, as the width 

 of the vein, the presence of flat and curved mica, of crystallized 

 feldspar, etc., that the time has not yet come for expressing an 

 opinion. These circumstances may depend more or less upon 

 the character of the walling; but if so, it is not known just what 

 the connection is. The same mav be said as to the influence of 

 width, depth, dip, strike, and accompanying minerals. 



Below the zone of atmospheric influences, rarely extending 

 below 20 feet, and sometimes not below 10 feet, the vein becomes 

 more solid, and the quality of the mica improves. The width 

 of the veins varies widely, from 3 to 40 feet, sometimes in the 

 same mine varying from 3 feet to 20 feet, as at the Presnel mine, 

 Yancey county. Nippiug of the vein is a common occurrence, 

 occasionally to almost entire obliteration. It has frequently hap- 

 pened that one set of miners have quit work on account of a 

 "nip," and another set at a subsequent date have prosecuted 

 the "driving," and found good mica within a few feet. The 

 "stringers" that make off' from the main vein penetrate into the 

 wall-rock at various angles, and though narrow sometimes yield 

 fine mica. 



The occurrence of well crvstallized feldspar is held to be a 



f A- 



sure indication of fine mica, though flesh-colored feldspar is re- 

 garded as exerting an injurious influence, as also the preponder- 

 ance of quartz, and the presence of uranium minerals. These 

 assertions must, however, be accepted with caution. 



ASSOCIATED MINERALS. 



The minerals found in mica veins are both numerous and in- 

 teresting. Some time before his ileath in 1885 the lamented W. 

 C. Kerr, for twenty years State Geologist of North Carolina, 

 prepared a list of the minerals found in mica veins, and this has 

 been corrected by F. A. Genth and one or two added by W. E. 

 Hidden. 



