MTCA    DEPOSITS    OF    WESTERN    NORTH    CAROLINA.  403 
The  quality  of  the  mica  obtained  from  different  localities  varies 
considerably.  In  general  it  may  be  said  that  the  mica  of  the  Cowee- 
Black  Mountain  belt  is  chiefly  clear  and  of  light  color  (as  a  rule  "  wine" 
or  "rum").  That  from  the  Blue  Ridge  belt  has  a  dark  smoky-brown 
color  and  much  of  it  is  more  or  less  "  specked."  In  much  of  the  Pied- 
mont belt  the  mica  is  of  good  quality  and  similar  to  that  of  the  Cowee- 
Black  Mountain  belt.  Of  course  there  are  exceptions  to  these  char- 
acteristics, in  part  connected  with  geologic  conditions  which  will  be 
mentioned  in  another  place  (p.  407). 
The  Cowee-Black  Mountain  mica  belt  is  in  the  heart  of  the  Appa- 
lachian Mountains.  The  deposits  lie  at  various  elevations  between 
2,000  feet  above  sea  level  and  that  of  the  highest  mountains,  or 
over  6,500  feet.  Some  are  high  up  on  the  rugged  slopes,  where  the 
soil  covering  is  thin.  Others  are  on  the  gentle  slopes  of  the  valleys, 
covered  by  deep  residual  clays.  Much  the  same  could  be  said  of 
the  Blue  Ridge  belt,  though  the  elevations  are  not  so  great.  In 
marked  contrast  with  the  high  relief  of  the  mountain  region  that 
includes  these  belts  is  the  topography  of  the  Piedmont  Plateau 
southeast  of  the  Blue  Ridge.  The  general  elevation  in  the  mica- 
bearing  areas  of  the  plateau  belt  is  from  1,000  to  '.,500  feet  above 
sea.  Though  typically  a  plateau,  it  is  more  or  less  dissected  by 
river  and  creek  valleys  200  or  300  feet  deep. 
The  rainfall  in  western  North  Carolina  is  heavy,  and,  as  the  cli- 
mate is  not  severe,  vegetation  flourishes,  and  large  areas  are  cov- 
ered with  dense  forests.  The  residual  soil  covering  due  to  rock 
decay  is  in  many  places  very  thick,  especially  where  the  slopes  are 
gentle  and  the  removal  of  decomposition  products  is  slow.  These 
features  combine  to  make  the  discovery  of  mica  deposits  difficult. 
GENERAL  GEOLOGY. 
The  mica-bearing  pegmatites  of  North  Carolina  are  found  chiefly 
in  rocks  of  Archean  age,  and  are  practically  confined  to  mica,  gar- 
net, cyanite,  hornblende,  and  granite  gneisses  and  schists.  Other 
rocks  m  the  region  are  granites,  diorites,  and  peridotites,  also  of 
Archean  age,  as  well  as  younger  granites,  volcanics,  and  sediments. 
The  metamorphism,  folding,  and  faulting  of  the  gneisses  and  schists 
have  been  extreme.  In  most  of  the  Archean  rocks  it  is  difficult  to 
determine  the  original  nature  of  the  formations,  since  much  of  the 
sedimentary  bedding  and  igneous  texture  has  been  destroyed  by 
mashing  and  recrystallization. 
The  majority  of  the  mica  deposits  occur  in  two  formations  as 
mapped  by  Keith, a  namely,  the  Carolina  gneiss  and  Roan  gneiss. 
The  Carolina  gneiss  includes  most  of  the  gneisses  and  schists  men- 
tioned above  that  are  not  hornblendic  in  composition.     The  Roan 
a  GeologicAtlas  U.  S.,Asheville  (116),  Cranberry  (90),  Mount  Mitchell  (124),  Nantahala  (143),  Pisgah 
and  Roan  Mountain  folios,  U.  S.  Geol.  Survey. 
