MICA    DEPOSITS    OF    WESTERN    NORTH    CAROLINA. 
417 
there  is  a  pegmatite  streak  from  1  to  2  feet  thick.  (See  fig.  17.)  In 
some  places  this  pegmatite  is  made  up  chiefly  of  mica;  in  others 
feldspar  with  some  quartz  is  equally  important.  The  contact  between 
the  pegmatite  and  granite  is  irregular  and  not  sharp.  Many  of  the 
mica  crystals,  especially  those  near  the  contact  with  the  mica  gneiss, 
have  their  cleavage  planes  normal  to  the  walls  of  the  pegmatite. 
They  do  not  exhibit  any  other  definite  orientation,  however.  The 
feldspar  has  been  kaolinized  to  some  extent  near  the  surface.  The 
mica  blocks  are  chiefly  small  (under  4  or  5  inches  in  diameter). 
They  have  a  clear  "rum"  color,  but  many  are  damaged  by  clay  stains 
between  the  laminae. 
They  are  plentiful, 
however,  and  yield 
much  punch  and  scrap 
material. 
A  pretty  example  of 
faulting  is  exposed  in 
this  mine.  The  mica 
streak  on  the  south- 
west side  of  the  granite 
has  been  brought 
nearly  opposite  that 
on  the  northeast  side 
by  a  fault  with  an 
8-foot  throw.  This 
fault  strikes  a  little  east  of  north  and  is  nearly  vertical.  The 
formations  on  the  east  side  of  it  have  slipped  to  the  north  a  few  feet, 
or  vice  versa. 
MINING   AND   TREATMENT   OF   MICA. 
The  methods  employed  in  working  most  of  the  mines  are  simple. 
Open  cuts  are  started  on  the  outcrop,  followed  by  shafts  or  tunnels 
when  the  "vein"  is  found  sufficiently  rich.  In  some  of  the  larger 
mines  power  drills  and  steam  pumps  are  employed  and  development 
proceeds  rapidly.  As  a  rule,  however,  simple  tools  are  used,  such  as 
pick  and  shovel  in  decomposed  formations  and  hand  drills  where  hard 
rock  is  encountered.  Dynamite  is  used  chiefly  in  breaking  down 
hard  rock.  The  "vein"  is  worked  out  by  shafts  (generally  inclined), 
tunnels,  drifts,  winzes,  and  stopes.  The  minimum  of  timbering  is 
used,  and  pillars  are  left  only  where  absolutely  necessary.  The 
workings  generally  have  a  very  irregular  shape,  since  they  follow  the 
mica  streaks  or  pockets  wherever  found.  Too  often,  in  the  past 
especially,  the  deposits  have  been  so  irregularly  worked  that  the 
term  "ground-hogging"  has  been  applied  to  the  methods  employed. 
"Ground-hog"  workings  consist  of  irregular  openings  ajt  the  surface, 
Fig.  17. — Section  of  pegmatite  at  Adams  mine,  H  miles  southeast 
of  Webster,  Jackson  County,  N.  C.  1,  Wall  rock  (mica  gneiss) ; 
2,  pegmatite,  mostly  mica;  3,  granite,  rather  fine  grained.  Dis- 
tance from  wall  to  wall,  7  feet. 
