weed.]  COPPER    PRODUCTION    OF    THE    UNITED    STATES  213 
each  of  the  great  copper-producing  districts  of  this  country  is  distin- 
guished by  a  characteristic  ore.  In  Michigan  it  is  native  copper;  in 
Montana,  chalcocite  (copper  glance)  or  enargite  (sulpharsenide  of 
copper)  ;  in  Arizona  it  is  largely  copper  oxides  and  carbonates;  in 
Tennessee  and  California,  chalcopyrite ;  in  Colorado,  tetrahedrite 
(gray  copper).  The  native  copper  of  Michigan  occurs  in  porous 
trap  sheets  and  in  interbedded  conglomerates  of  pre-Cambrian  age; 
the  rich  ores  of  Butte  occur  in  quartz -py rite  veins  in  Tertiary  gran- 
ite, while  the  great  deposits  of  Arizona  occur  chiefly  in  carboniferous 
limestones  about  Tertiary  igneous  masses.  The  differences  in  the 
character  of  the  ore  correspond  in  turn  to  very  different  modes  of  ore 
treatment,  and  this  corresponds  to  a  classification  of  the  ores  into 
native,  oxide,  and  sulphide  ores.  The  production  for  1903,  grouped 
in  this  way,  is  as  follows : 
Production  of  copper  in  the  United  States  in  1903. 
Pounds. 
Native    copper 192,  400,  577 
Copper   from   sulphide  ores '466,097,000 
Copper  from  oxide  ores,  siliceous  and  basic 40,648,271 
The  copper  production  of  Colorado,  amounting  to  4,158,368 
pounds,  is  derived  mainly  from  the  treatment  of  copper-bearing  sil- 
ver and  gold  ores  from  the  mines  of  Colorado  and  adjacent  regions. 
OXIDIZED    COPPER    ORES. 
The  only  places  where  oxidized  copper  ores  are  produced  in  large 
amount  are  the  Globe,  Clifton,  and  Bisbee  districts  of  Arizona.  At 
Bingham,  Utah,  six-tenths  of  1  per  cent  of  the  total  output  is 
oxidized  ore,  and  in  the  early  development  of  almost  all  (lie  great 
copper  mines  of  the  country  more  or  less  oxidized  ore  has  been  found. 
but  the  Arizona  districts  have  been  preeminently  deposits  of  oxidized 
ore,  and  it  is  only  in  recent  years  that  sulphide  ores  have  been  en- 
countered. The  oxidized  ore  is  of  two  kinds:  The  infusible — lean, 
siliceous,  oxidized  ores;  the  fusible — iron-bearing  or  calcareous  ores. 
The  advantages  of  smelting  and  bessemerizing  over  the  old  and 
wasteful  practice  of  smelting  oxide  ores  in  a  cupola  furnace,  with 
direct  reduction  to  black  copper,  has  led  to  the  endeavor  to  mix 
the  oxide  ores  with  those  carrying  sulphur,  and,  fortunately,  favor- 
able railroad  rates  have  been  secured  in  Arizona,  which  permit  an 
interchange  of  low-grade  ores.0  Thus,  Globe,  Ariz.,  ships  its  in- 
fusible, lean,  oxidized  ores  to  Bisbee  and  Douglas,  where  they  are 
used  for  converter  linings,  and  receives  in  return  the  sulphide  ores, 
which  are,  as  yet,  somewhat  scarce  at  Globe.  At  Clifton,  Ariz.,  but 
one   mine   supplies   any    amount    of   oxide   ores,    the    amount    being 
"James  Douglas,  Eng.  and  Miu.  Jour.,  Jan.  5,  1905,  p.  10. 
