50  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1906,    1'AHT    I. 
pyrrhotite.     Though  the  source  of  the   calcite   is   the  limestone  or' 
country  rock,  the  calcium  carbonate  has  migrated  to  a  certain  extent 
and  lias  been  redeposited  with  the  other  minerals. 
Gold  occurs  finely  disseminated  in  calcite,  quartz,  pyrite,  pyrrho- 
tite, and  chaleopyrite,  as  large  nuggets  associated  with  these  miner- 
als or,  less  commonly,  as  thin  sheets  following  the  cleavage  of  calcite. 
In  the  table  on  page  55  comparisons  are  made  of  the  minerals  of  the 
Cable  and  Granite-Bimetallic  mines. 
As  already  stated,  the  valuable  ore  deposits  are  confined  to  the 
sedimentary  rocks.  The  calcite  stringers  which  cut  the  granite  are 
small  and  of  low  grade  and  have  never  been  considered  of  economic 
value.  The  ore  is  so  irregularly  distributed  in  the  sedimentary  rocks 
that  the  entire  zone  is  regarded  as  the  vein,  and  must  be  prospected 
from  wall  to  wall  by  crosscuts  and  drill  boles  in  order  that  no  ore 
bodies  shall  la4  overlooked.  This  ore  zone  strikes  southeastward,  is^ 
rudely  tabular  and  nearly  upright,  and  has  been  partially  explore! 
underground  for  about  1,800  feet  along  its  strike;  on  the  surface  it 
appears  to  extend  farther  northwest  along  the  same  general  course! 
its  vertical  extent  is  unknown,  but  has  been  proved  for  about  (>()() 
feet.  On  the  tunnel  level  the  walls  or  granite  boundaries  are  for 
the  most  part  about  240  feet  apart  and  nearly  parallel.  The  contact 
plane  of  the  north  wall  dips  80°  to  90°  NE.  The  plane  of  the  south 
wall  is  very  irregular  and  from  the  tunnel  level,  near  the  engine  station, 
has  a  low  dip  northeastward  to  the  level  65  feel  below,  so  that  att 
this  point  the  ore  /one  is  onl\  about  80  feet  wide*  Below  the  65-fool 
level  the  contact  dips  again  to  the  southwest,  so  that  the  ore  /.one  is 
about  125  feel  wide  below  this  point,  on  the  21 4-fool  level."  The  out- 
line of  the  ore  zone  is  irregular  also  on  account  of  the  small  tongues  of 
granite  thai  project  into  the  limestone  and  the  blocks  of  granite  thai 
are  portions  of  such  tongues  detached  and  broken  by  subsequent 
movement . 
The  recrystallization  of  the  limestone  into  medium-grained  oi 
coarser  marble  is  general;  and  in  this  metamorphism  the  entire  ore 
zone  was  involved.  The  formation  of  the  coarse  calcite  or  ore  maj 
have  occurred,  to  a  considerable  extent,  along  structural  lines,  such 
as  planes  of  early  movement  and  bedding  planes,  but  if  so  these  were 
apparently  so  irregular  and  complex  that  they  can  now  be  traced  only 
in  exceptional  eases  and  then  only  for  short  distances.  On  the  2141 
foot  level  in  at  least  one  place  the  ore  followed  for  a  short  distance 
what  appeared  to  be  the  original  bedding  planes  of  the  limestone. 
That  the  coarsely  crystalline  calcite  or  ore  in  some  places  follows  lines 
of  movement  is  shown  on  the  tunnel  level,  just  east  of  the  entrance  to 
the  Lake  stope.  Here  three  flat,  nearly  horizontal  bodies  of  granite 
occur  at  different  elevations  and  in  positions  which  show   them  to  he 
a  Recent  drilling  shows  that  it  is  much  wider  than  thiseasl  of  the  shaft  on  this  level. 
