weed.]  COPPER    PRODUCTION    OP    THE    UNITED    STATES.  215 
wholly  of  native  copper,  which  requires  simply  melting  down  in  a 
furnace.  The  process  of  mechanical  concentration,  which  all  but 
the  "  mass  "  copper  undergoes,  is  peculiar  to  the  district.  The  ore  is 
pulverized  by  steam  stamps,  each  head  capable  of  handling  '250  tons 
of  ore  a  day,  the  resulting  product  being  classified  and  jigged  or 
passed  over  slime  tables,  etc.  The  cost  of  treatment  by  this  method 
varies  somewhat  with  the  different  ores  of  the  district,  but  is  cheap 
compared  with  ordinary  smelting,  and  permits  the  successful  working 
of  the  lowest  grade  ores  handled  anywdiere  in  the  world,  the  Atlantic 
mine  treating  ore  carrying  but  0.0  per  cent  copper  and  paying  divi- 
dends.    The  Calumet  and  Hecla  ore  averages  about  2.5  per  cent. 
SULPHIDE  ORES. 
Aside  from  the  Lake  Superior  and  Arizona  deposits  practically  all 
the  copper  ores  of  the  United  States  are  sulphides.  As  already 
stated,  the  most  common  copper-ore  mineral  the  world  over  is  chalco- 
pyrite,  usually  disseminated  through  pyrite  or  magnetic  pyrite.  Ore 
of  this  character  is,  moreover,  found  in  nearly  every  type  of  deposit. 
It  occurs  disseminated  through  igneous  rocks  and  in  the  contact  zones 
about  them,  in  quartz-pyrite  veins,  in  replaced  limestone,  and  is  the 
characteristic  mineral  of  the  great  lenses  of  cupriferous  pyrite. 
The  Eastern  or  Atlantic  border  States  contain  a  great  number  of 
copper  deposits  scattered  along  the  front  of  the  Appalachian  region 
from  Maine  to  Alabama.  The  only  deposits  now  being  worked  on  a 
large  scale  are  those  of  Ducktown,  Tenn.,  where  remarkably  low- 
grade  sulphide  ores  are  being  smelted  at  a  profit.  The  ore  bodies 
form  great  thick  lenses  in  crystalline  schists.  The  copper  occurs  as 
chalcopyrite  in  pyrrhotite  (magnetic  pyrite),  with  small  amounts  of 
country  rock  and  various  silicates.  The  ore  is  low  grade,  averaging 
less  than  2  per  cent  copper,  as  smelted.  Similar  ore  bodies  exist  at 
Ore  Knob,  N.  C,  at  various  places  in  southwestern  Virginia,  and  in 
Vermont,  but  are  not  worked.  Other  deposits  of  the  same  character, 
but  composed  essentially  of  pyrite,  carried  copper  ores  near  the 
surface.  This  gradually  disappeared  with  depth,  and  the  properties 
are  now  worked  for  the  pyrite  alone,  as  at  Tolersville,  Va.,  and 
Charlemont,  Mass. 
Copper-bearing  veins  are  worked  at  Virgilina,  Va.,  and  at  Gold 
Hill  and  elsewhere  in  Virginia  and  Georgia,  but  the  production  is 
small. 
The  Mississippi  Valley  contains  but  few  copper  deposits,  those  of 
Mine  La  Motte,  St.  Genevieve,  and  Sullivan,  Mo.,  being  the  best 
known.  The  product  is  small,  but  the  ores  carry  nickel  and  cobalt. 
They  are  described  by  H.  F.  Bain  and  E.  O.  Ulrich  on  pages  233-235 
of  this  bulletin. 
Montana. — The  enormous  amount  of  copper  produced  by  Montana 
