GOLD  AND  SILVER. 
In  addition  to  the  papers  here  included,  which  represent  the  results 
of  recent  work  by  the  Survey  in  important  precious  metal  mining 
districts,  other  reports  bearing  incidentally  on  the  subject  of  gold  and 
silver  will  be  found  under  the  head  of  "  Copper,"  on  pages  169  to  201. 
THE  JUNEAU  GOLD  BELT,  ALASKA, 
By  Arthur  C.  Spencer. 
INTRODUCTION. 
In  the  summer  of  1903  the  writer  and  Mr.  Charles  W.  Wright  made 
a  detailed  study  of  the  geology  and  mineral  resources  of  a  limited 
area,  including  the  Alaska-Treadwell  and  associated  mines  near  Juneau, 
Alaska.  In  addition  to  this  work,  visits  were  made  to  nearly  all  the 
mining  camps  of  the  mainland  portion  of  southeastern  Alaska,  between 
Windham  Bay,  about  75  miles  southeast  of  Juneau,  and  the  Porcupine 
placer  district,  in  the  Klehini  and  Salmon  river  basins  of  the  Chilkat 
River  drainage,  about  120  miles  to  the  northwest. 
The  Juneau  gold  belt  resembles  the  gold  belt  of  California  in  several 
ways.  Not  only  are  the  various  rocks  which  occur  in  this  part  of  south- 
eastern Alaska  similar  in  character  and  partly  equivalent  in  age  to  those 
forming  the  country  rock  of  the  Mother  Lode  district,  but  there  is  as 
well  a  definite  linear  distribution  of  some  of  the  gold-bearing  veins 
parallel  with  the  general  strike  of  the  bed-rock  formations,  though,  as 
in  the  neighborhood  of  the  noted  systems  of  veins  in  the  California 
gold  belt,  there  are  many  independent  deposits  lying  outside  the  main 
complex  of  lodes. 
Prospecting  has  been  in  progress  in  different  parts  of  this  belt  since 
1870,  but  the  main  incentive  to  vigorous  exploration  came  with  the 
discovery  of  the  Gold  Creek  placers  and  the  founding  of  Juneau  in 
1880.  Several  early  attempts  to  work  gold  veins  occurring  adjacent 
to  the  productive  placers  in  the  Silver  Bow  Basin,  at  the  head  of  Gold 
Creek,  were  unsuccessful,  the  first  mine  to  be  put  upon  a  productive 
basis  being  the  Alaska-Treadwell,  on  Douglas  Island,  about  2  miles 
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