COPPER    MINES    OF    THE    UNITED    STATES MONTANA.  113 
The-  older  veins  are  distinctively  replacement  veins,  and  consist  of  quartz  and  pyrite 
with  secondary  glance  ores.  They  are  surrounded  by  areas  of  granite  altered  by  sol f atari c 
action. 
The  output  consists  of  glance-pyrite-quartz  ores,  often  of  high  grade,  and  of  the  altered 
granite  impregnated  with  glance  and  pyrite.  The  bulk  of  the  material  mined  is  concen- 
trating ore, carrying  3  to  4  per  cent  of  copper, 55  percent  of  silica,  and  16  per  cent  of  iron. 
Many  of  the  lesser  veins  in  the  eastern  part  of  the  district  consist  of  nearly  solid  enargite 
and  pyrite.  The  Parrot  and  Original  ores  carry  much  bornite.  The  ores  contain  silver, 
the  quantity  varying  from  1  ounce  to  1  per  cent  of  copper  in  the  Trenton  to  one-fourth 
ounce  to  1  per  cent  in  the  eastern  part  of  the  district.  The  ores  average  about  0.0375 
ounce  silver  and  $2.25  per  ton  of  gold.  The  veins  carry  high-grade  ores  to  exceptional 
depths.  The  Anaconda  carries  rich  glance  ore  at  2,200  feet;  the  Original  has  enargite- 
bornite-glance  ore  at  2,000  feet;  the  Diamond,  Mountain  Con,  and  High  Ore  at  2,000  feet. a 
DEVELOPMENT. 
During  the  year  1905  the  copper  output  for  Montana  reached  the  enormous  total  of 
335,000,000  pounds.  With  the  exception  of  a  small  production  from  scattered  properties, 
;his  great  output  comes  from  the  copper  mines  of  the  Butte  district.  During  the  year 
several  important  discoveries  and  developments  have  been  made.  The  Pittsburg  and 
Montana  Copper  Company,  operating  in  the  flat  between  the  city  of  Butte  and  the  East 
3idge,  has  opened  up  four  veins  on  the  1,200-foot  level,  and  is  now  producing  5,000  tons  of 
)re  a  month,  and  the  furnaces  are  producing  copper  from  the  company's  own  ores.  This 
company  has,  it  is  understood,  abandoned  the  attempt  to  use  the  Garretson  process,  and  is 
smelting  its  siliceous  Butte  ores  with  pyrrhotite  from  the  Spring  Hill  mines  situated  south  of 
Helena.  In  converting  the  matte  raw  siliceous  ore  is  charged  directly  into  a  molten  matte 
Baggally  process),  a  basic  lining  to  the  converter  being  used.  This  is  a  marked  change 
rom  ordinary  practice,  in  which  siliceous  linings  are  used. 
The  discovery  of  these  veins  in  what  has  hitherto  proved  a  barren  portion  of  the  district 
las  greatly  stimulated  activity  in  the  vicinity  of  the  mines.  Several  new  companies  have 
oeen  formed  to  take  over  properties  in  this  part  of  the  district,  and  active  exploitation  is 
promised  in  1906. 
The  North  Butte  Copper  Company  was  formed  during  1905,  and  acquired  the  Speculator, 
£dith  May,  Jessie,  and  other  properties.  A  crosscut  driven  north  developed  ore  bodies  of 
ohenomenal  size  and  richness  in  the  Edith  May  and  Jessie  veins.  These  ore  bodies  mark 
.he  farthest  known  limit  of  the  rich  copper  ores  of  the  district,  and,  as  noted  later,  occur 
iinder  conditions  which  have  awakened  widespread  interest  in  the  possible  extension  of  the 
topper-bearing  zone  to  the  north.  In  the  western  portion  of  the  copper-producing  section 
lie  Lexington  mine,  now  controlled  by  the  United  Copper  Company,  has  yielded  consider- 
able high-grade  copper  ore.  but  this  has  been  of  a  different  character  from  the  ore  of  the 
copper  belt,  consisting  mainly  of  chalcopyrite,  an  unusual  mineral  in  the  copper  mines 
Proper. 
i  The  Raven  mine,  which  lies  north  of  the  Buffalo  and  is  in  the  extreme  northwestern  part 
>f  the  copper  belt,  has  also  yielded  considerable  amounts  of  copper  ore,  and  the  Snoozer 
laim  of  this  company  is  being  extensively  prospected  and  developed  from  the  crosscut  on 
tie  1,500-foot  level  driven  from  the  Buffalo  shaft. 
j  In  the  great  mines  of  the  camp  the  workings  have  been  deepened,  with  marked  success. 
Fhe  most  notable  instance  is  in  the  Anaconda  mine,  where  the  shaft  has  been  deepened  to 
):,400  feet  and  the  crosscut  from  the  2,200-foot  level  encountered  rich  ore  on  the  middle 
dge.  This  "  strike  "  has  been  widely  heralded  in  the  newspapers.  On  the  2,400-foot  level 
lihe  crosscut  had  not  reached  the  vein  at  the  beginning  of  1906. 
o  See  description  in  Nature  of  Ore  Deposits,  a  treatise  on  the  Ore  Deposits  of  the  World,  by  Beck  and 
Veed,  p.  223. 
