100  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
The  Bisbee  district  is  in  the  central  part  of  the  Mule  Mountains,  a  few  miles  north  of  the 
Mexican  line. 
The  principal  ore  bodies  lie  south  of  and  within  a  mile  of  Bisbee.  They  occur  in  Carbon- 
iferous limestone,  on  the  southwest  side  of  a  great  northeast-southwest  fault,  closely  asscH 
elated  with  a  boss  of  granite-porphyry.  The  limestones  form  a  synclinal  basin  cut  across  the' 
center  by  the  fault.  The  ore  occurs  in  roughly  sheet-like  masses  more  or  less  parallel  to  the 
bedding  of  the  limestone  and  mostly  within  1,000  feel  of  the  fault  or  the  granite-porphyry 
intrusion.  Under  the  town  (he  ore  comes  to  the  surface  and  is  worked  down  to  100  feet,  but 
it  occurs  at  increasing  depth  to  the  southeast ,  and  in  the  Calumet  and  Arizona  mine  was  first 
found  at  a  depth  of  800  feet,  thus  indicating  that  the  depth  of  the  ore  increases  toward  the 
center  of  the  local  basin  formed  by  the  beds,  though  it  is  not  con  lined  to  any  one  horizon.    ] 
Thus  far  all  the  ore  bodies,  save  the  extreme  western  ones  of  the  Copper  Queen,  lie  in  the 
Carboniferous  limestones.  Though  these  flat  ore  bodies  lie  with  the  bedding,  their  occur- 
rence is  dependent  on  other  feat  ures.  Large  masses  of  low-grade,  partly  Oxidized  pyrite  Oil 
Occur  along  the  contact  bet  ween  porphyry  and  limestone.  ( )t  her  huge  ore  bodies  turn  down 
alongside  porphyry  dikes,  and  fissures  in  the  limestone  influence  distribution  of  the  ore.  The 
disseminated  pyrit  ic  ore  of  t  he  mam  porphyry  mass  of  Sacrament  o  Hill  has  not  so  far  proved 
workable. 
The  "cave"  ores  of  malachite,  azurite,  etc  ,  for  which  Bisbee  was  so  long  famous,  are  now 
exhausted.  The  ores  now  mined  consist  of  pyrite,  with  variable  amounts  of  chalcocite  and 
chalcopyrite.     There  is  an  observed  relation  between  permeability  and  good  ore. 
Ransome,  in  his  report,  pointed  out  the  probable  occurrence  of  the  then  unknown  ore 
bodies  south  of  the1  porphyry  boss  in  the  following  words: 
It  may  be  pointed  ou1  thai  less  than  half  of  the  semicircular  mineralized  zone  (Bonanza  circle)  a  I  tout 
i  lie  porphj  ry  mass  of  Sacramento  1 1  ill  has  been  explored  al  all.  *  *  *  There  still  remains  an  exten- 
sive area  of  unknown  bul  promising  ground  lying  south  of  Sacra  men  to  Hill  and  extending  easl  ward 
toward  the  southeastern  continuation  of  the  Dividend  fault,  an  area  here  concealed  by  the -Glance  j 
conglomerate. 
But,  judging  from  surface  indieat  ions,  t  here  lias  been  considerable  mineralization  of  the  Naeo  lime- 
stone south  of  Sacramento  Bill,  and  there  is  nothing  improbable  in  the  occurrence  of  high-grade  ores  in 
this  limestone  a1  stral  [graphically  higher  horizons  than  those  in  which  ore  bodies  have  hitherto  beej 
found. 
Recent  work  by  the  Copper  Queen  Company  along  the  Czar  fault,  a  feature  not  known 
prior  to  the  work  of  Ransome  for  this  Survey,  has  led  to  the  discovery  of  new  ore  bodies. 
Coconino  County  contains  a  small  producing  copper  mine  near  the  Grand  Canyon.  The 
geology  of  this  mine  was  treated  by  S.  F.  Emmons  in  the  Economic  Bulletin  for  1904. a 
GLOBE    DISTRICT. 
The  principal  mines  of  the  Globe  district,  Gila  County,  are  the  Old  Dominion  and  United 
Globe  properties,  the  Summit  group,  and  the  Buffalo  Mountain.  There  were  11  producing 
properties  in  1904.  The  mines  produce  about  3,400  tons  a  month,  having  an  average  value 
of  about  SIN  a  ton.  The  gold  content  is  insignificant,  amounting  to  but  a  few  cents  a  ton,' 
and  the  silver  content  but  slightly  more. 
The  mines  of  the  Globe  district  have -been  further  developed,  the  output  for  t  he  year  1905 
approximating  28,500,000  pounds,  which  includes  some  custom  ore,  and  about  5,500,000 
pounds  of  copper  from  the  Copper  Queen  mine  shipped  to  Globe  as  sulphide  ore  to  mix  with 
the  oxidized  ores.  The  change  in  smelting  from  the  old  method  of  treating  oxidized  ores 
direct  to  the  modern  practice  of  matte  smelting  and  bessemerizing  has  led  to  an  increased 
output  and  decreased  costs.  The  concentrating  mill  built  by  the  Old  Dominion  Company 
and  put  in  operation  in  August,  1905,  will  add  materially  to  the  output,  and  the  draining 
of  the  deeper  levels  will,  according  to  Doctor  Douglas,  reopen  rich  ore  bodies  inaccessible 
for  some  time  past. 
a  Bull.  U.  S.  Geol.  Survey  NTo.  260,  1905,  pp.  230-231. 
