.       MICA    DEPOSITS    OF    WESTERN    NORTH    CAROLINA.  405 
Some  of  the  more  persistent  pegmatites  occupy  straight  fissures 
that  hold  their  direction  for  some  distance.  Elsewhere  they  are 
folded  with  the  country  rock  or  bent  and  twisted  into  various  shapes. 
Many  are  more  or  less  conformable  with  the  bedding  of  the  gneisses 
and  schists.  In  the  latter  case  they  are,  in  a  large  measure,  subject 
to  the  deformations  of  the  country  rock.  In  many  places,  however, 
(lie  pegmatites  are  conformable  for  some  distance,  and  then  branch 
out,  cutting  from  one  layer  to  another  across  the  bedding.  Locally 
there  is  an  elbowing  or  bulging  out  on  one  wall,  without  a  similar 
irregularity  on  the  other  wall  of  the  pegmatite.  It  is  not  uncom- 
mon for  pegmatite  masses  to  cut  across  the  country  rock  for  long 
distances. 
Though  pegmatites  have  been  worked  for  mica  in  regions  of  horn- 
blende gneiss  and  hornblende  schist,  where  they  are  directly  asso- 
ciated with  those  rocks,  the  majority  of  the  deposits  are  in  small 
biotite-gneiss  or  schist  masses  included  in  the  hornblende  areas. 
Where  the  pegmatite  is  in  contact  with  hornblende  gneiss,  the  latter 
may  be  highly  biotitic. 
Pegmatites  occur  in  irregular  masses,  streaks,  lenses,  augen,  or 
balls,  some  of  them  having  no  visible  connection  with  other  pegma- 
tite bodies.  They  range  from  a  fraction  of  an  inch  up  to  many  yards 
in  thickness.  The  limit  of  size  below  which  they  can  not  be  profitably 
worked  for  mica  might  be  placed  arbitrarily  at  from  1  to  2  feet  for 
rich  and  regular  "  veins/'  In  the  very  large  pegmatites  the  mica  is 
not  in  general  evenly  distributed  through  the  mass,  but  is  richer  in  one 
portion  than  another,  so  that  the  entire  bulk  of  the  rock  does  not  have 
to  be  removed  in  mining.  The  irregularities  of  pegmatites  and  the 
consequent  difficulties  in  mining  mica  from  them  are  well  illustrated 
in  road  cuts  or  similar  excavations  where  pegmatized  gneiss  or  schist 
has  been  cut  into.  The  lenticular  shapes,  pinching  and  swelling, 
crumpling,  folding,  and  faulting  to  be  observed  in  these  cuts  are 
found  to  be  nearly  duplicated  in  larger  pegmatites  opened  for  mica. 
As  stated  before,  these  smaller  masses  may  grade  into  those  containing 
mica  of  commercial  value.  Here  and  there  the  two  can  be  seen  at  the 
same  locality. 
Horses  or  inclusions  of  wall  rock  are  common  in  pegmatites. 
Some  of  them  are  in  the  form  of  bands  or  sheets  parallel  to  the  walls, 
-and  the  schistosity  of  these  bands  is  also  parallel  to  the  walls.  They 
range  from  an  inch  or  two  up  to  a  couple  of  feet  in  thickness  and  their 
length  may  be  many  times  their  width.  Elsewhere  they  occur  as 
irregular-shaped  masses  from  a  few  inches  up  to  several  feet  thick. 
If  the  bedding  has  been  preserved,  it  may  lie  at  any  angle  with  that  of 
the  inclosing  wall  rock.  In  some  places  the  horses  are  partially  peg- 
matized by  streaks  of  pegmatite  ramifying  through  them  and  the 
development  of  considerable  feldspar  and  quartz  through  their  mass. 
