COPPER    MINES    OF    THE    UNITED    STATES ARIZONA.  101 
The  production  of  the  Globe  copper  camp  comes  mainly  from  one  mine — the  Old  Domin- 
ion. According  to  Ransome,a  who  made  a  detailed  study  of  the  region,  the  chief  product  ion 
of  the  district  is  from  ore  bodies  in  limestone  and  shattered  quartzite,  with  lesser  amounts 
from  stringer  lodes  in  diabase  (pyrite  ores  of  the  Old  Dominion  and  the  Grey  mines)  and 
replacements  of  dacite  tuff  (Black  Copper  mine). 
The  important  ore  bodies  of  the  district  are  all  in  limestone  and  quartzite,  and  lie  on  the 
southeast  side  of  the  great  displacement  which  separates  the  sediments  from  diabase  and  is 
known  as  the  Old  Dominion  fault.  The  limestone  is  350  to  550  feet  thick  and  rests  on  the 
quartzite.  The  ore  bodies  in  limestone  are  rudely  lenticular  in  shape  and  roughly  parallel 
with  the  level  beds  of  the  limestone.  They  occur  at  various  horizons,  but  always  along- 
side of  or  near  the  master  fault.  The  largest  ore  body  was  200  by  100  feet  and  60  feet  thick. 
The  ore  of  these  great  masses  is  all  oxidized.  Other  ore  bodies  consist  of  impregnations  of 
shattered  or  permeable  rock,  quartzite,  or  tuff,  the  ore  passing  into  sulphides  in  depth. 
There  is  an  evident  association  of  the  ores  and  faulting,  and  a  genetic  relation  of  ore  and 
igneous  rocks. 
The  Old  Dominion  shaft  is  827  feet  deep  (1904).  The  Grey  mine  is  on  an  extension  of  the 
Old  Dominion  fault. 
In  the  Pinal  district  the  Black  Warrior  and  other  mines  have  already  increased  their 
output  and  are  expected  to  become  important  producers  in  the  current  year. 
The  Saddle  Mountain  Mining  Company,  whose  property  is  located  near  Gila  River,  close 
to  Dudleyville  and  near  the  San  Carlos  Indian  Reserve,  has  entered  the  list  of  copper  pro- 
ducers. Its  smelter  was  blown  in  in  August,  1905,  and  is  now  in  successful  operation, 
treating  250  tons  a  day.  The  property  of  this  company  includes  a  considerable  acreage 
that  shows  large  areas  of  oxidized  ore  occurring  in  altered  limestones  adjacent  to  igneous 
intrusions.  The  development  close  to  the  porphyry  contact  shows  sulphide  ores  with 
masses  rich  in  magnetite,  this  latter  ore  carrying  approximately  8  per  cent  copper  present 
as  chalcopyrite.  The  company  is  expected  to  produce  continuously  during  1906,  and  as 
the  combination  of  garnetiferous  ore,  magnetite  ore,  sulphide  ore,  and  limestone  affords 
a  favorable  fluxing  mixture,  an  enlargement  of  the  plant  in  the  near  future  has  been  con- 
fidently predicted. 
The  main  shaft  is  now  330  feet  deep.  The  ore  has  an  average  of  3  per  cent  copper. 
The  product  for  the  year  1905  was  356.8  tons  of  matte,  carrying  394,318  pounds  of  copper, 
90.98  ounces  of  gold,  and  3,527  ounces  of  silver,  with  a  total  value  of  $52,124. 
CLIFTON-MORENCI    DISTRICT. 
The  copper  mines  of  Graham  County  yield  relatively  low-grade  ores,  having  an  average 
value  for  the  year  1904  of  but  $7.84  per  ton.  The  Clifton-Morenci  district  (Greenlee  and 
Copper  Mountain  districts)  is  the  only  producer  of  importance.  The  Arizona,  Detroit, 
Shannon,  Federal,  and  Standard  companies  own  the  principal  properties,  the  last  named 
being  the  only  one  not  having  reduction  works. 
The  Clifton  district  has  not  shown  an  increase  in  production,  owing  to  serious  inter- 
ruption by  floods.  Both  the  companies  operating  in  this  district  have  had  construction 
work  under  way  to  increase  the  capacity  of  the  concentrators.  The  Arizona  Copper  Com- 
pany and  the  Detroit  Copper  Company  both  show  large  ore  reserves. 
Morenci  ranks  next  to  Bisbee  as  a  copper-producing  center,  the  output  for  1905  being 
about  60,000,000  pounds.  The  ores  now  mined  average  between  3  and  4  per  cent  copper. 
About  20  per  cent  is  smelting  ore,  carrying  6  to  10  per  cent  copper,  and  the  balance  is 
concentrating  ore.  The  Shannon  and  Arizona  companies,  operating  at  Metcalf,  are  min- 
ing both  oxidized  and  concentrating  sulphide  ores.  The  bulk  of  the  ore  mined  is,  however, 
a  sulphide.  The  workings  are  all  comparatively  shallow,  the  deepest  shaft  being  but 
400  feet  (1903). 
a  Ransome,  F.  L.,  Geology  of  the  Globe  Copper  district,  Arizona;  Prof.  Paper  U.  S.  Geol.  Survey  No. 
12,  1903. 
