GRANITE-BIMETALLIC    AND    CABLE    MINES,   MONTANA.  51 
broken  pieces  of  a  larger  mass;  the  lines  of  faulting  by  which  they 
were  separated  have  been  entirely  obliterated  and  the  blocks  are  now 
surrounded  by  coarse  calcite;  the  planes  where  the  faults  once 
passed  show  no  signs  of  movement,  but  are  completely  recemented 
by  coarse  calcite,  in  every  way  resembling  that  which  surrounds  the 
granite  blocks  elsewhere.  Since  the  faulting,  the  recrystallization 
has  been  complete. 
The  primary  ore  is  the  coarse  calcite  carrying  a  variable  amount  of 
quartz,  pyrite,  chalcopyrite,  pyrrhotite,  arsenopyrite,  magnetite,  hem- 
atite (specularite),  and  gold.  These  minerals  appear  to  have  been 
deposited  at  the  same  time  and  each  of  them  has  been  noted  in  the  lower 
levels  of  the  mine.  The  metallic  minerals  as  a  rule  occur  as  irregular 
masses  in  the  spar  and  quartz,  but  locally  as  bands  alternating  with 
them.  In  this  ore  the  gold  is  for  the  most  part  finely  disseminated  in 
the  rock,  but  rich  ore  containing  masses  of  gold  larger  than  a  grain 
of  wheat  has  been  found  on  the  lowest  level  of  the  mine.  Some  of 
the  larger  bodies  of  gold  "may  be  of  primary  origin.  A  mine  speci- 
men as  big  as  a  walnut  contains  about  half  pyrrhotite  and  half  gold. 
The  association  of  oxides  and  sulphides  is  common  in  all  of  the  ores 
from  all  parts  of  the  mine.  In  the  lowest  level  copper  ore  is  found 
in  which  films  of  bornite  and  chalcocite  coat  masses  of  chalcopyrite. 
There  is  a  considerable  quantity  of  this  ore  along  the  north  granite 
contact  on  the  214-foot  level. 
The  oxidized  ore  has  so  far  proved  the  richest  of  the  mine.  This 
occurs  near  the  tunnel  level  and  in  the  ground  above  it  and  is  charac- 
terized by  a  large  amount  of  hematite  and  limonite.  It  contains 
more  silica  and  less  calcite  than  the  sulphide  ores.  Some  of  the 
oxidized  ores  from  the  upper  workings  carried  considerable  copper, 
and  several  thousand  tons  of  tailings  from  ore  milled  years  ago,  before 
the  present  mill  was  built,  were  found  to  pay  handsomely  when 
smelted  for  their  copper  content.  The  average  of  analyses  of  seven 
cars  of  these  tailings  shipped  to  the  Anaconda  smelter  is  as  follows: 
Average  analysis  of  tailings  from  the  upper  and  partly  oxidized  ores  in  Cable  mine. 
Silver ounces  per  ton. .     0. 15 
Gold per  ton. .  $2.  97 
Copper per  cent . .      3.  00 
Insoluble  matter do 19. 1 
FeO do 38.  3 
CaO do....  10 
Moisture do 11.2 
C02  (estimated) - do 8 
Tailings  from  sulphide  ores  milled  later  and  from  lower  levels  do  not 
carry  such  high  values  in  copper,  so  it  appears  that  there  was  a 
copper-enriched  zone  in  the  upper  part  of  the  mine.  The  sulphide 
copper  ore  on  the  2 14-foot  level  is,  however,  still  richer  in  copper  than 
the  tailings  from  the  ore  near  the  surface. 
