36  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.        [ bull.  260. 
The  important  belt  of  gold-quartz  veins  of  California  extends 
northward' into  Oregon  and  Alaska,  the  principal  quartz  mines  of 
which,  beyond  much  doubt,  are  of  the  same  Mesozoic  age.  In  Cali- 
fornia the  output  of  this  belt  has  evidently  increased  somewhat  dur- 
ing 1904,  and  is  estimated  to  be  $13,400,000,  against  $12,059,725  in 
1903.  The  quartz  mines  in  the  southern  and  northeastern  part  of 
Oregon  have  maintained  their  production,  which  will  be  about  $1| 
100,000.  Alaska  coast  mines  are  credited  with  $3,200,000,  while  the 
scattered  Mesozoic  veins  in  Idaho  have  yielded  only  about  $000,000 
The  total  yield  of  the  Mesozoic  gold-quartz  mines  of  the  Pacific  coasli 
belt  should  be  $21,000,000. 
While  the  Mesozoic.  belt  of  gold-quartz  veins  appears  chiefly  ir 
connection  with  intrusive  rocks  of  the  types  of  quartz-monzonites 
granodiorites,  and  diorites,  there  is  another  great  class  of  gold 
bearing  veins  of  distinctly  Tertiary  age,  which  are  contained  chief!} 
in  effusive  rocks,  such  as  andesites,  rhyolites,  basalts,  and  phonolites 
Most  of  these  veins  have  been  deposited  since  the  Miocene  epoch  anc 
form  a  fairly  well-defined  group,  with  several  subdivisions.  The^ 
are  not  as  a  rule  smelting  ores,  rich  in  copper  and  lead,  althougl 
some  of  them  contain  much  pyrite;  speaking  from  a  smelting  stand 
point,  they  would  be  classified  as  dry  ores.  These  younger  veins  seen 
to  be  especially  characterized  by  great  richness  of  ore  in  bonanza 
near  the  surface.  Their  production  may  be  estimated  at  $35,T00,00C 
the  largest  item  in  the  geological  distribution  of  the  output.  Call 
fornia's  tribute  from  the  gold  belt  at  the  eastern  foot  of  the  Sierr 
Nevada  remains  about  the  normal  figure  of  $800,000.  Nevada  ha: 
greatly  increased  its  product,  chiefly  by  the  new  camps  of  Tonopal 
and  Goldfield,  the  production  from  the  latter  having  approximate 
$2,000,000  since  its  discovery  in  January,  1904.  The  Comstock  stilil 
yields  a  few  hundred  thousand  dollars  a  year.  Practically  all  o< 
Nevada's  gold  has  been  derived  from  Tertiary  veins,  although  som 
small  deposits  may  be  older. 
Idaho  contributes  about  $700,000  from  Silver  City  and  De  LamaiJ 
in  Owyhee  County,  also  from  Thunder  Mountain  and  various  place} 
in  Custer  County.     Montana  yielded  $1,200,000  from  the  recently  d( 
veloped    resources    in    Fergus    County.     South    Dakota's    "  siliceoi  ; 
ores  "  produce  about  $2,270,000.     The  greatest  increase  comes  froi 
Colorado,  where  the  combined  output  of  the  Cripple  Creek,  Gilph 
and  San  Juan  veins  amounts  to  about  $21,000,000,  an  increase  c  l| 
several  millions  over  last  year.     With  considerable  doubt  $2,200,0C  j 
of  Utah's  gold  has  been  classed  in  this  group,  divided  chiefly  betwee 
the  Mercur  mines,  in  Tooele  County,  and  the  newly  discovered  Ann 
Laurie  mine,  in  Piute  .County.     Little  is  known  about  the  gold-pr< 
ducing  mines  of  Arizona;  many  of  them   certainly   belong   in   th 
class,  and  $2,100,000  of  their  gold  has  been  credited  to  it. 
