192  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
to  Finlay,  grade  into  quartz  veins,  and  are  accompanied  by  dikes  of 
black  trap  rocks  (camptonites). 
General  character  of  the  deposits.— The  deposits  of  the  Vermont 
copper  belt  occur  as  lenticular  masses  in  foliated  micaceous  schists. 
They  therefore  simulate  the  type  known  as  bedded  deposits,  being 
apparently  entirely  conformable  to  the  schistosity  of  the  inclosing 
rocks.  The  outcrops  are  generally  concealed,  however,  except  where 
the  bed  is  exposed  by  mining  operations.  The  ore  forms  lenses  of 
varying  horizontal  extent  and  thickness,  and  these  lenses  overlap,  so 
that  in  going  down  a  lens  wedges  out,  but  the  tapering  bottom  of  one 
lens  overlies  the  upper  end  of  another.  This  feature  was  observed  at 
the  Copperfield  mine  and  at  the  Union  mine  in  Corinth. 
The  ore  bodies  sometimes  show  a  clearly  denned  foot  wall,  but  more 
commonly  show  transitions  into  the  adjacent  rock.  As  a  rule  the  foot 
wall  is  more  regular  than  the  hanging  wall,  the  latter  showing  frequent 
undulations. 
The  horizontal  extent  of  the  ore  lenses  varies  considerably  at  the  dif- 
ferent mines,  and  indeed  in  the  different  lenses  of  the  same  mine.  The 
ore  body  at  the  Elizabeth  mine  has  been  extracted  for  700  feet  hori- 
zontally, and  in  the  Ely  mine  a  lens  over  100  feet  across  has  been 
mined.  Along  its  strike  the  ore  mass  may  either  end  in  a  blunt  wedge, 
sometimes  showing  a  mere  film  continuing  along  the  horizon,  or  the 
ore  may  fork  into  rapidly  thinning  wedges,  or  simply  grade  into 
country  rock  by  an  increasing  amount  of  "slaty"  material.  The 
horizon  of  this  Elizabeth  ore  body  is  traceable  for  nearly  a  mile,  and 
another  ore  body  (Reynolds)  is  found  on  its  continuation  li  miles 
northward. 
The  thickness  varies  at  different  localities.  At  the  Elizabeth  mine~ 
the  ore  was  as  much  as  100  feet  wide  in  the  open-cut  workings,  and  on 
the  225-foot  level  is  35  feet  between  walls.  The  ore  has  a  maximum 
width  of  12  feet  at  the  Union  and  adjacent  properties  in  Corinth 
Township,  and  of  20  feet  at  the  Copperfield  property. 
The  depth  to  which  these  deposits  extend  is  not  known.  At  the  Ely 
mine  the  inclined  shaft  is  3,400  feet  long.  As  already  noted,  the  ore 
body  consists  of  several  lenses,  so  that  one  lens  may  pinch  out;  but  in 
the  Union  and  Ely  mines  the  ore  continues  in  overlapping  lenses  to 
the  greatest  depth  attained. 
The  ore  bodies  are  remarkably  free  from  water.  At  a  depth  of 
3,400  feet  on  the  dip  or  1,500  feet  vertical  the  Ely  ore  body  is  very 
dry,  the  water  of  the  mine  being  confined  to  a  few  hundred  feet  of 
upper  workings.  The  ore  and  incasing  rock  are  very  solid  in  all  the 
mines  and  practically  no  timbering  is  used. 
<h<  i  racter  of  ore. — The  ore  consists  of  pyrrhotite  (magnetic  p}^rite 
of  iron,  locally  mundic)  with  scattered  grains  and  irregular  masses  of 
chalcopyrite,  and  small  amounts  of  pyrite  and  of  zinc  blende.  The 
gangue  minerals  consist  of  quartz,  actinolite,  garnet,  and  other  meta- 
