lindgren.]     PRODUCTION    OF   SILVER  IN"   UNITED   STATES  IN   1904.  41 
from  Tertiary  quartz  veins  carrying  gold  and  silver  ore,  in  some  cases 
silver  exclusively.  This  is  an  important  source  of  production,  and 
when  it  is  taken  as  a  whole  the  contrast  between  the  amount  of  silver 
derived  from  this  source  and  that  obtained  from  other  veins  is  really 
very  remarkable.  The  production  is  divided  chiefly  between  Colo- 
rado, Nevada,  and  Montana.  Arizona  produces  a  great  deal  of  silver 
from  this  class  of  deposits,  but  the  statistics  do  not  permit  an  accurate 
estimate  of  the  amount.  It  is  believed  to  be  in  the  neighborhood  of 
1,500,000  ounces.  California  adds  200,000  ounces,  derived  from  gold- 
silver  veins  in  the  belt  at  the  eastern  base  of  the  Sierra  Nevada.  Col- 
orado contributes  2,000,00°  ounces,  principally  derived  from  the  San 
Juan  country  and  the  Gilpin  district,  bu:  with  scattered  additions  by 
many  other  counties.  Idaho  yields  700,000  ounces,  approximately, 
from  the  gold-silver  veins  in  Owyhee  County,  and  a  small  amount 
from  deposits  in  the  central  part  of  the  State,  notably  in  Custer 
County.  The  amount  contributed  by  Montana  is  very  much  in  doubt, 
owing  to  the  difficulty  of  classifying  the  veins  in  that  State.  At  any 
rate  it  is  not  likely  to  exceed  1,000,000  ounces.  Practically  the  whole 
of  the  silver  production  of  Nevada,  4,5)0.000  ounces,  belongs  under 
this  heading.  The  amount  of  silver-lead  ores  now  mined  in  that 
State  is  very  small  indeed.  Utah  produces  3G0,000  ounces  from  dry 
ores.  The  source  and  age  of  many  of  these  are  very  doubtful,  and  it 
is  possible  that  a  part  of  this  amount  should  really  be  credited  to 
gold-quartz  veins  and  deposits  of  earlier  age. 
The  siliceous  ores  of  South  Dakota  contain  considerably  more  sil- 
ver than  does  the  principal  Cambrian  deposit  of  the  Homestake 
mine,  in  the  same  State.  From  this  source  138,000  ounces  are  added. 
The  total  amount  of  silver  derived  from  the  Tertiary  gold-quartz 
veins  and  allied  deposits  in  1904  would  be  approximately  11,000,000 
ounces.  This  probably  represents  a  small  decrease  from  the  figures 
of  1903,  due  to  a  decreased  production  in  Colorado  owing  to  various 
labor  troubles. 
COPPER  ORES. 
It  is  a  fact,  which  is  perhaps  scarcely  realized,  that  one-third  of 
the  production  of  silver  in  the  United  States  is  derived  as  a  by-prod- 
uct from  the  smelting  of  copper  ores,  the  larger  part  of  which  do  not 
contain  enough  silver  to  be  classed  as  paying  silver  ores.  By  far 
the  largest  amount  is  supplied  by  Montana,  and  nearly  the  whole 
amount  of  this  is  derived  from  the  Butte  copper  ores,  which  occur  in 
fissure  veins  traversing  granitic  rocks  and  are  believed  to  be  of  early 
Tertiary  age.  The  copper  smelted  in  Arizona  usually  carries  very 
little  silver.  The  ores  of  the  United  Verde  mine,  however,  contain  a 
certain  amount  of  both  gold  and  silver.  From  this  and  other  smaller 
sources  a  total  of  1,300,000  ounces  is  obtained  for  Arizona.     The  age 
