GRANITE-BIMETALLIC    AND    CABLE    MINES,  MONTANA.  41 
Ruby  and  Blaine  shafts,  the  vein  carried  high-grade  secondary  silver 
ore,  whereas  on  level  8,  just  below  this  ore,  it  was  composed  of  rhodo- 
chrosite  and  quartz,  cut  by  a  large  number  of  veinlets  of  zinc  blende, 
chalcopyrite,  and  quartz.  Here  the  rhodochrosite  and  early  quartz 
is  distinctly  older  than  the  zinc  blende  and  chalcopyrite,  for  the 
vein  was  opened  and  locally  brecciated  in  the  interim  between  the 
deposition  of  these  minerals.  At  this  place  the  zinc  blende  and  the 
chalcopyrite  are  related  to  the  earlier  minerals  in  the  same  way  thai 
ruby  silver  is  above,  and  appear  to  play  a  similar  role.  It  is  probable 
that  they  were  deposited  at  the  same  time,  but  that  the  zinc  blende 
and  chalcopyrite  were  carried  down  farther  at  this  point  by  the  sec- 
ondary solutions.  By  far  the  larger  portion  of  the  dividends  which 
the  mine  has  paid  came  from  the  exploitation  of  the  secondary  sul- 
phide ore. 
Enriched  oxidized  ore. — Above  the  zone  of  enriched  sulphides  is  a 
zone  of  enriched  oxidized  ore,  for  the  most  part  between  the  100-foot 
and  400-foot  levels,  but  in  a  few  places  extending  to  the  surface  and  at 
one  place  extending  downward  as  far  as  level  '.).  This  ore  is  composed 
of  quartz  stained  with  iron  and  manganese  oxides  and  less  commonly 
with  copper  carbonates.  Cerargyrite  and  native  silver  occur  as  thin 
seams  cutting  through  the  quartz  or  as  films  plastered  on  the  outside 
of  crushed  quartz  fragments.  Associated  with  this  ore  is  a  little 
argentite  and  pyromorphite ;  galena,  zinc  blende,  pyrite,  and  chalco- 
pyrite are  of  local  occurrence.  This  ore  runs  from  300  to  400  ounces 
of  silver  and  from  $5  to  $16  in  gold.  The  value  of  this  oxidized 
zone  is  in  general  less  than  that  of  the  enriched  sulphides. 
Poor  oxidized  ore. — Extending  from  the  surface  down,  in  places  as 
far  as  300  feet  or  more,  is  a  zone  of  poor  oxidized  ore,  consisting  of 
quartz,  for  the  most  part  broken  and  stained  with  iron  and  manganese 
oxides.  It  contains  some  lead  carbonate,  malachite,  azurite,  chrvso- 
colla,  pyromorphite,  pyrite,  and  galena.  It  carries  less  than  40  ounces 
of  silver  and  only  a  lit  tie  gold  and  has  never  been  exploited  with  profit . 
This  portion  of  the  vein  was  so  unpromising  that  the  claims  were  once 
abandoned  by  prospectors,  before  the  richer  ores  were  discovered. 
This  oxidized  zone  has  resulted  from  incomplete  oxidation  of  the 
secondary  sulphides.  The  apex  of  this  zone,  which  is  the  apex  of  the 
vein,  has  been  leached  of  the  greater  part  of  its  silver  and  gold  values, 
and  this  leaching  appears  to  have  extended  in  a  few  places  as  far  as 
400  feet  below  the  surface.  The  presence  of  sulphides  in  this  ore, 
however,  shows  that  even  here  the  oxidation  is  not  complete.  Small 
bunches  of  galena,  with  which  a  little  argentite  is  probably  associated, 
occur  here  and  there  in  this  zone  and  are  unoxidized  remnants  of  sec- 
ondary sulphides.  Some  massive  low-grade  pyrite,  which  shows  no 
sign  of  postmineral  crushing,  occurs  similarly  at  this  horizon  and  ma}^ 
