134  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
small  values  in  silver  and  gold,  though  it  contains  no  unaltered  galena.  Small  amounts 
of  galena  were  also  found  in  several  other  prospect  holes  in  this  vicinity,  in  which  the 
relations  are  similar  to  those  already  described  and  which  need  not  therefore  be  mentioned 
in  detail. 
In  T.  45  N.,  R.  6  E.,  about  10  miles  in  a  direct  line  S.  60°  E.  from  the  prospects  just 
described,  a  similar  occurrence  of  galena  in  quartzite  was  examined.  Here  a  gray  quartz- 
ite  containing  sidcrite  and  galena  lies  nearly  horizontal,  but  is  cut  by  a  number  of  parallel 
joints  which  strike  N.  70°  W.  Considerable  prospecting  was  done  several  years  ago  in 
sec.  3,  T.  45  N.,  R.  4  E.,  and  two  of  the  old  tunnels  are  still  open.  The  rocks  here  arei 
broken  by  a  system  of  vertical  joints  which  strike  N.  70°  E.  There  is  no  evidence  of  dis- 
placement along  these  joints,  but  several  of  them  contain  quartz  veins,  the  largest  of 
which,  about  6  inches  wide,  thins  down  to  nothing  in  a  distance  of  40  feet.  The  quartz 
is  honeycombed  with  iron-stained  cavities  and  contains  some  weathered  pyrite.  Pros- 
pectors report  that  the  unweathered  ore  contained  galena,  and  that  there  was  also  a  large 
ledge  or  "blow-out"  of  galena  ore  exposed  in  the  creek  bed  at  a  point  now  covered  with 
gravel.  Galena-bearing  rocks  were  reported  by  many  witnesses  from  other  localities, 
and  though  most  of  these  were  not  examined  by  the  writer  it  may  reasonably  be  believed 
from  the  evidence  presented  that  such  minerals  are  widely  distributed.  As  far  as  observed 
the  rocks  in  which  these  ores  occur  belong  in  the  Coeur  d'Alene  series,  and  probably  for 
the  most  part  in  the  Wallace  formation.  The  prevailing  strikes,  both  of  the  bedding 
planes  and  of  the  most  definite  systems  of  jointing  and  cleavage,  are  approximately  N. 
70°  W.  Samples  of  such  ores  taken  from  seven  different  localities  were  assayed  for  lead: 
and  silver,  and  though  none  of  them  were  found  to  carry  values  sufficient  to  make  them 
commercial  ores  under  present  conditions,  all  showed  the  presence  of  more  than  traces  of* 
these  metals  in  the  average  proportion  of  one-third  of  an  ounce  of  silver  to  1  per  cent  of 
lead.  In  the  Coeur  d'Alene  district  this  proportion  is  about  one-half  an  ounce  of  silvtr 
to  1  per  cent  of  lead,  and  it  is  evident,  therefore,  that  these  ores  are  somewhat  lower  in] 
silver  than  those  of  the  Coeur  d'Alene  district.  The  only  sample  collected  by  the  writer 
which  was  tested  for  gold  was  found  to  carry  0.02  ounce  of  gold  to  1  per  cent  of  lead. 
From  the  testimony  of  a  number  of  o.ther  witnesses  who  have  had  analyses  made  of  oresl 
from  this  region  it  seems  to  be  true  that  generally  these  ores  are  richer  in  gold  than  the: 
lead-silver  ores  of  the  Coeur  d'Alene  district. 
COPPER    DEPOSITS. 
Copper  ores,  some  of  which  are  in  valuable  deposits,  are  well  distributed  over  the  whole 
district.  These  probably  occur  in  several  of  the  Coeur  d'Alene  formations,  and  although 
they  are  all  connected  with  definite  fractures  or  lines  of  faulting  they  present  some  variety 
in  their  occurrence.  The  most  important  series  of  prospects  is  found  in  a  belt  about  6 
miles  wide  extending  for  about  16  miles  southeast  from  Stevens  Peak  along  the  Montana- 
Idaho  boundary.  A  great  deal  of  development  work  has  been  done  in  this  belt,  since  it 
is  easily  accessible  from  points  on  the  Northern  Pacific  Railway.  The  ore  bodies  here  are 
deposited  in  fault  fissures  which  strike  approximately  east  and  west.  Although  the 
intrusive  masses  of  diabase  already  mentioned  are  common  in  this  vicinity,  none  of  the 
copper-bearing  ledges  have  been  definitely  connected  with  them.  These  ledges  are  for 
the  most  part  contained  in  rocks  which  probably  belong  to  the  Wallace  formation  and 
the  displacements  along  the  fissures  are  probably  not  very  great.  Croppings  of  the  veins 
are  usually  indicated  by  heavy  "iron  caps,"  which  sometimes  project  above  the  surface, 
forming  what  are  locally  called  "blow-outs."  The  gossan  usually  consists  of  breccia 
derived  from  the  wall  rocks  cemented  by  hematite  and  limonite.  It  usually  contains 
the  copper  carbonates,  malachite  and  azurite.  At  greater  depths  the  ore  is  still  mixed 
with  broken  country  rock,  but  the  vein  matter  consists  of  calcite,  siderite,  and  some  quartz, 
with  more  or  less  sulphides  of  copper  and  iron.  In  one  instance  galena  and  chalcopyrite 
are  present  in  nearly  equal  amounts,  but  usually  galena  is  not  present.  Nearly  all  these 
ores  carry  considerable  gold. 
