108  CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,  1905. 
Mining  and  Milling  Company  has  driven  a  crosscut  tunnel  2,500  feet  long  to  cut  an  aurifer- 
ous copper  vein. 
Boise  County  produced  but  500  pounds  of  copper  in  1904,  as  a  by-product  of  gold  ores 
shipped  to  custom  smelters. 
Custer  County  was  formerly  the  largest  copper  producer  of  the  State,  the  production 
for  1904  being  2,734,489  pounds,  valued  at  $341,811.  This  came  from  the  mines  of  the 
White  Knob  Copper  Company,  of  the  Alden  Creek  district,  now  shut  down,  and  from 
the  Loon  Creek  district.     The  production  for  1905  was  684,134  pounds. 
The  White  Knob  ore  deposit  a  occurs  on  a  contact  between  granite  and  limestone. 
The  ore  zone  is  400  feet  wide  and  1,200  feet  long,  and  contains  chalcopyrite,  pyrite,  and 
a  little  galena,  together  with  magnetite  and  hematite  in  an  altered  limestone  composed 
of  garnet  and  calcite.  The  oxidized  zone  is  600  feet  deep.  The  White  Knob  smelter 
was  shut  down  in  1905.  Recent  development  has  shown  the  existence  of  payable  bodies 
of  sulphide  ore  beneath  the  ore  oxidized  zone  and  the  mine  is  again  actively  worked. 
An  important  development  of  copper  ore  has  been  made  at  Loon  Creek,  where  the 
Lost  Packer  Mining  Company  owns  a  fissure  vein  in  granite  and  rhyolite.  The  vein  is 
10  to  15  feet  wide  and  carries  a  pay  streak  about  2  feet  wide  that  is  clean  and  well  defined. 
The  ore  consists  of  massive  chalcopyrite,  with  20  per  cent  of  copper  and  about  2  ounces 
of  gold.  Outside  of  the  pay  streak  the  vein  is  of  low  grade,  running,  it  is  said,  about  3 
per  cent  of  copper  and  $5  to  $7  gold.  A  blast  furnace  capable  of  handling  100  tons  daily 
has  recently  been  installed. 
The  Paymaster  copper  mine,  in  the  Skull  Canyon  district,  Fremont  County,  works  a 
deposit  on  a  contact  between  limestone  and  quartzite. 
Lemhi  County  produced  about  5,000  pounds  of  copper  in  1904,  occurring  in  gold  and 
silver  ores. 
Shoshone  County  produced  5,805,000  pounds  of  copper,  of  a  value  of  $893,389,  in  1905. 
The  only  productive  copper  property  of  the  Cceur  d'Alene  district  is  the  Snowstorm 
mine,  cast  of  Mullan.  The  deposit  occurs  in  Algonkian  (Revett)  quartzite,  and  is,  accord- 
ing to  Ransome,  an  impregnated  cupriferous  zone  conforming  to  the  bedding  planes, 
the  strike  being  N.  60°  W.  and  the  dip  65°  SW.  The  ore  body  varies  from  10  to  35  feet 
in  width,  and  is  reported  to  be  430  feet  long.  The  ore  carries  chalcopyrite,  bornite,  and 
chalcocite  in  disseminated  particles  in  the  quartzite.  The  quartzite  is  not  particularly 
fissured  and  does  not  appear  to  differ  from  the  rock  of  the  foot  and  hanging  walls.  The 
greater  part  of  the  mineralized  quartzite  contains  about  4  per  cent  of  copper,  with  6  ounces 
of  silver,  and  0.1  ounce  of  gold  per  ton.  The  ore  shipped  is  worth  $9  to  $10  per  ton,  the 
Butte  and  Tacoma  smelters  giving  a  freight  and  treatment  rate  of  $5  when  SiO2=90  per 
cent.     A  leaching  plant  is  reported  to  have  been  erected  on  the  property  in  1905. 
Washington  County  produced  898,209  pounds  of  copper  in  1904,  valued  at  $112,276. 
This  output  came  from  the  Seven  Devils  district,  the  Landore  smelter  of  the  Ladd  Metal 
Company  and  the  smelter  at  Sumpter,  Oreg.,  treating  the  ore.  The  chief  producing  mines 
are  those  of  the  Blue  Jacket  Consolidated  Copper  Company  and  the  Montana-Nebraska 
Copper  Company,  but  small  amounts  were  also  produced  by  the  Peacock,  White  Monument, 
Helena,  Queen,  Alaska,  and  Crescent.     According  to  Lindgren,  the  ores  occur  as  follows: 
In  the  Seven  Devils  district  and  in  the  adjacent  Snake  River  canyon  copper  deposits  are  very  abun- 
dant. There  is,  in  that  vicinity,  an  extensive  series  of  Triassic  basic  lavas,  with  intercalated  layers  of 
slate  and  limestone.  There  are  also  diorites,  intrusive  in  these  beds.  All  of  these  igneous  rocks  appa- 
rently contain  copper  which  was  easily  concentrated  into  deposits  of  various  kinds— some  fissure  veins, 
others  zones  of  impregnation,  others  contact  deposits. 
In  the  locality  of  the  original  discovery  in  the  Seven  Devils  the  copper  occurs  in  typical  contact 
deposits.  Small  masses  of  limestone  are  embedded  in  a  later,  intrusive  diorite;  at  the  contact  and 
usually  in  the  limestone  are  found  irregular  bodies  and  bunches  of  bornite,  chalcocite.  and  a  little  chal- 
copyrite, containing  about  10  ounces  of  silver  and  a  little  gold  per  ton.  The  limestone  at  the  contact  is 
very  crystalline  and  contains,  associated  with  the  ores,  abundant  garnet,  epidote,  quartz,  calcite,  and 
specularite.     The.  copper  sulphides,  as  shown  by  their  intergrowth,  were  certainly  formed  at  the  same 
a  Lindgren,  W.,  Character  and  genesis  of  certain  contact  deposits:  Trans.  Am.  Inst.  Min.  Eng.,  1901.  \ 
