COPPER   MINES    OF    THE    UNITED    STATES ARIZONA.  103 
nated  with  copper  sulphides  along  the  limestone  contact.  The  ores  consist  of  pyrite,  with 
chalcopyrite  and  occasional  bornite,  but  there  is  also  a  copper-bearing  silver-lead  ore  con- 
sisting of  galena,  zinc  blende,  and  chalcopyrite,  a  combination  difficult  of  reduction.  The 
Mammoth  mine  is  500  feet  deep  and  the  Union  shaft  350  feet  deep.  A  railroad  21  miles 
in  length  has  been  built  from  Silver  Bell  to  a  connection  with  the  Southern  Pacific.  Though 
the  mine  is  equipped  with  a  smelting  plant,  the  production  for  the  last  year  has  been  shipped 
mainly  to  the  smelter  at  Douglas. 
Yavapai  County,  which  includes  the  Jerome  district,  with  the  famous  United  Verde 
mine  and  the  various  copper  properties  to  the  south  of  Jerome,  has  maintained  its  position 
as  an  important  copper  producer  throughout  the  year.  Unlike  the  other  copper  ores  of 
the  Territory,  those  of  the  Jerome  district  contain  relatively  high  values  in  gold  and  silver. 
The  average  ore  treated  at  the  smelters  had  a  value  of  $18.95  per  ton,  and  the  copper  ores 
produced  3,854  ounces  of  gold  in  1904.  The  ore  body  is  supposed  to  be  a  columnar  but 
wide  mass  of  sulphides  in  a  shear  zone  in  diorite. 
The  Equator  Mining  and  Smelting  Company,  whose  smelter  is  situated  8  miles  south  of 
Jerome,  was  a  regular  producer  for  a  few  months  only  and  is  now  shut  down. 
The  Bradshaw  Mountain  Copper  Company  and  the  American  Copper  Company,  with 
numerous  adjacent  properties,  are  in  the  Bradshaw  Mountains  district. 
The  results  of  the  survey  of  the  Bradshaw  Mountains  quadrangle  are  given  in  Folio 
No.  126  of  the  Geologic  Atlas  of  the  United  States.  The  following  extract  from  this  folio 
relates  to  the  copper  deposits  of  this  much-advertised  region : 
No  copper  deposits  of  proved  extent  and  value  are  yet  known  in  this  district,  but  several  promising 
prospects  were  seen.  Two  types  of  copper  deposit  were  recognized.  One  consists  of  distinct  veins 
carrying  chalcocite,  chalcopyrite,  tetrahedrite,  and  in  some  instances  bournonite,  with  a  gangue  of 
quartz,  fluorite,  and  barite. 
The  sulphide  minerals  are  largely  altered  at  the  surface  to  chrysocolla  and  malachite.  These  veins 
carry  silver  values,  as  well  as  copper. 
The  second  type  consists  of  impregnation  zones  in  schist,  chalcopyrite,  pyrite,  and  bornite,  with 
more  or  less  quartz,  replaced  chlorite  schist  or  amphibolite,  forming  bodies  of  irregular  and  indefinite 
outline.  Small  stringer  veins  carrying  the  same  minerals  are  also  present  in  places,  but  the  formation 
as  a  whole  appears  to  be  a  direct  replacement. 
The  surface  zones  of  such  deposits  are  silicious  schists,  pitted  and  copper  stained  with  films  of  native 
copper  and  sometimes  of  cuprite.    Small  gold  values  are  also  found  in  these  deposits. 
The  Valverde  smelter,  which  operates  on  ores  from  this  district,  was  rebuilt  in  1905. 
The  Big  Bug  district,  also  in  the  Bradshaw  Mountains  region,  has  a  small  but  increasing 
production,  and  the  ores  contain  considerable  gold  and  silver.  The  1904  production  was 
86.934  pounds. 
Copper  deposits  a  similar  to  those  of  the  Kaibab  Plateau  t>  occur  in  the  White  Mesa,  in 
the  Navajo  Indian  Reservation,  125  miles  north  of  Flagstaff  and  50  miles  east  of  the  Kai- 
bab Plateau.  The  Triassic  red  sandstone  is  here  less  than  200  feet  thick  and  is  overlain  by 
200  to  250  feet  of  white  sandstone,  forming  the  White  Mesa.  The  white  sandstone  is  cross- 
bedded.  The  color  is  white  or  gray,  rarely  red.  The  rock  is  composed  of  well-worn  grains 
of  quartz  sand  from  which  most  of  the  cementing  material  has  been  leached  out,  leaving  it 
soft  and  friable.  The  copper  deposits  consist  of  a  replacement  of  the  cement  of  one  par- 
ticular cross-bedded  stratum  of  the  sandstone  by  chrysocolla,  with  some  tenorite  in  grains 
or  masses.  Specimens  contain  as  much  as  32  per  cent  of  copper.  Generally  the  copper 
deposits  are  a  few  hundred  cubic  feet  in  size,  and  no  strict  line  of  demarcation  is  shown 
between  them  and  the  surrounding  sandstone,  the  bluish-green  color  of  the  chrysocolla 
gradually  fading  into  the  white  of  the  sandstone.  The  ore  is  apparently  associated  with 
small  vertical  crevices  or  fissures.  Some  of  the  deposits  show  a  distinct  vein  structure, 
while  others  do  not.     The  source  of  the  ore  is  not  very  clear. 
a  Described  by  H.  F.  Lunt,  Trans.  Am.  Inst.  Min.  Eng.,  1903. 
b  Described  by  E.  P.  Jennings,  Trans.  Am.  Inst.  Min.  Eng.,  1903. 
