COPPER   MINES    OF    THE    UNITED    STATES CALIFORNIA.        105 
Hill  district  and  Devonian  shales  and  limestones  in  the  Iron  Mountain  belt.  The  dike 
rocks  cutting  the  lavas  are  connected  with  granitic  intrusions  and  may  be  genetically 
related  to  the  ore  deposits.  The  ore  bodies  occur  in  shear  zones,  the  rock  sheeting  and 
crushing  being  due  to  mountain  uplift  which  formed  the  Sierra  Nevada  and  Klamath 
Mountains  at  the  close  of  Jurassic  time.  The  shear  zones  are  of  limited  extent,  less  than  a 
mile  long  and  from  a  few  inches  to  20  feet  wide,  with  vertical  or  steep  westerly  dip  and 
a  north-south  course. 
In  the  Bully  Hill  district  there  are  three  zones,  two  of  them  parallel,  a  few  hundred  feet 
apart,  with  valuable  ore  bodies.  The  westernmost  is  in  the  Bully  Hill  metarhyolite;  the 
other  is  a  metabasalt  dike  near  the  surface,  following  the  dike  contact  to  a  known  depth  of 
500  feet. 
The  Bully  Hill  ore  is  base,  carrying  zinc,  antimony,  etc.  It  is  said  to  average  8  per  cent 
and  to  carry  $2  to  $3  in  gold  and  silver.  The  ore  bodies  are  stoutly  lenticular,  varying 
from  mere  nodules  to  masses  hundreds  of  feet  long  and  wide.  They  occur  regularly  dis- 
tributed in  the  crushed  and  mostly  impregnated  rock  of  a  shear  zone  4  to  100  feet  wide, 
averaging  about  30  feet.  All  gradations  may  be  seen,  from  unmineralized  crushed  rock 
through  partial  replacements  and  impregnations  to  complete  replacement.  The  ore  bodies 
pitch  to  the  north.  They  are  usually,  though  not  always,  marked  by  outcrops  of  porous 
limonite  or  gossan  ore,  but  sometimes  by  merely  stained  rock.  The  gossan  retains  its 
gold  values. 
The  Bully  Hill  ores  consist  of  chalcopyrite  with  bornite  and  chalcocite,  a  gangue  of  barite, 
so  finely  disseminated  as  to  be  invisible.  Copper  glance  is  common  in  the  dark  ore.  There 
are  three  lodes — the  Delamar,  Anchor,  and  Copper  City.  The  first  named  is  developed  by 
a  tunnel  800  feet  beneath  the  outcrop,  and  the  "vein"  is  developed  for  100  feet  in  length. 
The  Anchor  lode  is  200  feet  west  of  the  Delamar,  runs  N.  10°  E.,  is  vertical,  and  lies  in 
silieified  rhyolite,  locally  called  quartzite.     Nothing  is  known  of  the  Copper  City  lode. 
The  Iron  Mountain  district  contains  the  mine  of  the  same  name,  together  with  the 
Shasta  King  and  Mammoth. 
The  copper  production  of  California  comes  mainly  from  the  workings  of  the  Iron  Moun- 
tain mine  near  Keswick,  owned  by  the  Mountain  Copper  Company.  The  sulphide  ores  of 
this  mine,  which  contain  much  excess  iron,  have  long  been  useful  as  affording  a  means  of 
treatment  for  the  dry  gold  and  silver  ores  of  the  surrounding  country.  The  damage  caused 
by  smelter  fumes,  however,  led  to  numerous  damage  suits,  and  the  reduction  of  the  ore  will 
be  hereafter  accomplished  mainly  at  the  new  plant,  where  sulphuric  acid  will  be  manu- 
factured and  fertilizer  made  as  a  by-product. 
The  Mountain  Copper  Company's  ores  occur  as  great  lenses  lying  in  schists  formed  by  the 
alteration  of  igneous  rocks.  A  pronounced  fault  separates  the  eastern  ore  body  from  the 
western.  The  ores  consist  of  pyrrhotite,  with  pyrite  and  chalcopyrite  and  considerable 
zinc.  The  production  is  approximately  1,300,000  pounds  of  copper  a  year,  the  ore  aver- 
aging about  4  per  cent. 
The  main  ore  body  is  said  to  be  from  100  to  400  feet  wide,  800  feet  long,  and  500  feet 
deep,  and  was  covered  with  gossan  cappings  100  to  300  feet  thick.  The  ore  averages  about 
5  per  cent  copper,  with  2  ounces  silver,  or  slightly  less  than  $1  per  ton. 
The  company  also  owns  the  Hornet  mine,  which  is  in  a  large  body  of  pyritic  ore,  carrying 
2  to  1\  per  cent  copper,  but  with  47  to  57  per  cent  sulphur.  The  Bessemer  copper  is 
shipped  to  the  New  Jersey  Metal  Refining  Works  at  Elizabeth,  N.  J.,  owned  by  the  com- 
pany, where  the  metal  is  refined  and  the  gold  and  silver  extracted.  The  output  for  1905 
was  somewhat  less  than  for  previous  years,  owing  to  the  construction  of  the  new  reduct  ion 
plant.     The  ore  bodies  occur  in  northeast-southwest  shear  zones. 
The  ore  has  declined  from  an  average  of  7.45  per  cent  copper  in  1897  to  5  per  cent  in 
1901,  with  2  ounces  silver  and  less  than  $1  gold  per  ton  of  ore.  The  ore  is  low  in  silica 
and  free  from  arsenic,  bismuth,  etc.  The  more  northern  ore  bodies  of  this  copper  belt 
are  of  lower  grade  than  those  of  Iron  Mountain. 
