2 JOURNAL OF THE 



and sometimes they are largely concentrated in the 

 middle of the vein, or, it may be, distributed throug'h- 

 out the dike with a considerable degree of uniformity. 

 In many cases the crystals are too small and few to 

 permit of the working of the vein as a mica mine; in 

 other cases very little mica is present, and the feldspar 

 constitutes the larger part of the material. This feld- 

 spar of the dikes undergoes, throug-h the weathering 

 action of the atmosphere, certain chemical chang-es re- 

 sulting* in its alteration from feldspar into kaolinite — 

 the kaolin of commerce. 



These dikes vary considerably in size, rang'ing from 

 a few inches to several hundred feet in thickness, and 

 up to many hundred yards in length. They are gene- 

 rally parallel to the schistosity of the crystalline rocks, 

 which, however, in some cases, they cross at various 

 angles. 



The kaolin in those dikes which occur in the* Unaka 

 or Smoky mountains is said to have been mined by the 

 Indians, "packed" across the countr}^ to the seaboard, 

 and shipped to England as early as the l7th century. 

 From one of them, near Webster in Jackson Connty, 

 kaolin is now mined (by the Harris Clay Co.) and 

 shipped to Trenton, N. J. and other centers for the 

 manufacture of fine pottery. This Webster dike con- 

 tains very little mica and com.paratively little quartz. 

 It has a maximum width of about 300 feet, and has 

 been traced for a length of more than a half mile. It 

 is mined to a depth of from 60 to 120 feet, below which 

 the original feldspar has not been sufficiently altered, 

 and is too hard for economic mining*. The kaolin is 

 brought from the mine, crushed, and washed in a se- 

 ries of settling-vats, for the purpose of separating 

 it from the granular quartz. Its plasticity is increased 



