136  CONTKIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
Montana  boundary,  the  copper  prospects  are  scattered  and  undeveloped.  Several  copper- 
bearing  ledges  along  St.  Joe  River  below  the  crossing  of  the  De  Borgia  trail  are  reported 
by  prospectors,  but  these  have  not  been  examined  by  the  writer,  though  specimens  oB 
copper  ore  consisting  of  chalcopyrite  and  quartz  were  found  in  the  gravels  in  St.  Joe  Riverj 
near  the  point  where  the  De  Borgia  trail  crosses.  A  rather  promising  copper  prospect 
in  which  the  ore  consists  for  the  most  part  of  carbonates  is  reported  from  T.  42  N.,  R.  8.  E.,' 
near  the  southern  boundary  of  this  district. 
In  T.  45  N.,  R.  3  E.,  there  is  a  group  of  copper  prospects,  some  of  which  have  been 
partially  developed.  They  occur  for  the  most  part  in  a  white  quartzite,  which  may  be] 
identical  with  the  Revett  formation,  and  near  some  masses  of  intrusive  granite.  The 
best  known  of  these,  -ailed  the  Black  Prince,  is  situated  at  the  mouth  of  Black  Prince.] 
Creek,  in  section  10,  and  is  developed  by  two  short  tunnels,  but  it  has  been  abandoned 
for  several  years.  The  ore  body  consists  of  brecciated  quartzite,  having  the  interstices 
filled  with  vein  quartz  which  contains  a  considerable  amount  of  bornite,  chalcopyritJ 
and  pyrite.  Some  well-defined  joints,  one  of  which  seems  to  mark  the  wall  of  the  ore 
body,  strike  N.  65°  W  On  the  dumps  of  this  tunnel  there  are  several  tons  of  rather 
promising  ore,  but  the  face  of  the  tunnel  shows  only  narrow  stringers  of  ore,  surrounding 
the1  fragments  of  quartzite.  Two  samples,  one  taken  from  the  face  of  the  tunnel  and  the 
other  from  the  surface  croppings,  were  assayed,  showing  the  presence  of  copper  and  gold, 
but  no  trace  of  silver.  Copper-stained  debris  has  been  found  for  several  miles  northwest! 
from  the  Black  Prince,  and  near  Big  Creek,  which  joins  St.  Joe  River  in  section  5,  there 
are  several  partially  developed  prospects,  some  of  which  promise  to  yield  copper  ores, 
while  others  may  lead  to  deposits  of  lead  and  silver  or  gold.  The  prospects  examine! 
show  a  large  deposit  of  gossan,  in  which  neither  galena  nor  stains  of  copper  were  recognized. 
Assays  of  samples  taken  at  random  showed  small  amounts  of  gold  and  silver,  but  no  trace 
of  copper.  Prospectors  interested  in  the  development  of  these  claims  report  that  the 
assays  which  have  been  made  range  from  80  cents  to  $10.75  in  gold.  The  development 
has  not  progressed  far  enough  to  show  tin  course  of  the  veins.  Near  them,  however 
there  are  outcrops  of  breccia  indicating  a  fault  which  strikes  X.  70°  W.,  and  it  is  probable 
that  the  course  of  the  heavily  mineralized  deposits  just  described  will  be  found  to  be 
parallel  with  it.  To  the  north  of  this  place,  for  several  miles  along  Big  Creek,  in  T.  56  N., 
R.  3  E.,  there  are  reported  to  be  prospects  showing  carbonates  of  coppei .  but  these  were  not 
examined  by  the  writer. 
In  T.  43  N.,  R.  4  E.,  considerable  prospecting  has  been  done  on  a  vein  carrying  pyrite, 
chalcopyrite,  and  bornite  in  white  quartz.  From  the  testimony  of  other  witnesses  this 
seems  to  be  a  well-defined  vein  traceable  for  400  or  500  feet  in  a  northeast-southwest 
direction,  and  contained  between  walls  of  schistose  quartzite,  which  is  probably  equivalent 
ti>  the  Revett  quartzite  of  the  Coeur  d'Alene  district.  The  vein  is  reported  to  be  about, 
10  feet  wide  and  is  developed  by  several  open  cuts  and  a  tunnel  36  feet  long.  An  average  < 
sample  of  the  ore  taken  across  the  ledge  is  said  to  have  yielded  $2.48  in  gold,  silver,  copper, 
and  lead.  A  picked  sample  which  was  assayed  for  the  writer  was  found  to  contain  &i 
trace  of  gold,  0.8  ounce  silver,  and  2.1  per  cent  of  copper.  Copper  ores  have  been  reported 
by  prospectors  from  many  other  parts  of  this  region,  but  except  in  the  localities  described 
there  have  been  no  attempts  at  development  and  the  prospects  were  not  examined. 
PLACER-GOLD    DEPOSITS. 
This  region  has  been  prospected  more  or  less  for  placer  gold  for  the  past  forty  years, 
and  although  there  are  placer-mining  districts  a  short  distance  away  on  nearly  all  sides, 
attempts  to  locate  valuable  deposits  of  this  kind  have  here  been  unsuccessful.  In  the 
surrounding  regions  placer  gold  is  mined  at  Murray  a  in  the  Cceur  d'Alene  district,  at 
Tyson,  about  10  miles  west  of  the  southwest  corner  of  this  district ;  near  Dent  and  Orofino,b 
aRansome,  F.  L.,  op.  cit.,  pp.  299-300.  bLindgren,  Waldemar,  op.  cit.,  pp.  84-85. 
