ORE  DEPOSITS  OF  THE  COEUR  D'ALENE  DISTRICT.  IDAHO. 
By  Frederick  Leslie  Kansome. 
INTRODUCTION. 
Although  the  Coeur  d'Alene  region  of  northern  Idaho  producer 
more  argentiferous  lead  ore  than  any  other  district  in  the  United! 
States,  its  geological  features  are  comparatively  little  known.  Lind- 
gren  °  has  published  brief  accounts  of  some  of  the  mines  and  has, 
described  the  principal  mineralogical  features  of  a  few  of  the  ores> 
Finlay  h  has  given  a  good  general  description  of  the  lodes  and  miness 
mainly  from  the  technical  standpoint,  and  has  devoted  about  a  page 
to  the  geology  of  the  region.  These  are  the  only  important  publica- 
tions relating  to  the  geology  of  this  part  of  Idaho  that  have  appeared 
The  detailed  investigation  of  the  district  by  this  Survey  was  begin 
in  1900  with  the  construction  of  a  topographic  map  by  V.  H.  Mam 
ning,  topographer,  known  as  the  Coeur  d'Alene  special  map.  This 
the  first  accurate  map  of  the  mining  area,  is  on  the  scale  of  1 :  625(1 
(approximately  1  mile  to  the  inch),  with  contour  intervals  of  5( 
feet.  It  covers  the  region  lying  between  47°  25'  and  47°  40'  nortl 
latitude  and  115°  40'  and  116°  10'  west  longitude,  and  is  the  equiva 
lent  of  two  of  the  usual  fifteen-minute  quadrangles  of  the  Geologi 
Atlas  of  the  United  States.  The  area  mapped  is  about  23J  mile 
from  west  to  east  and  about  171  miles  from  north  to  south.  Thi 
topographic  map  was  completed  in  1902,  and  geological  field  won 
was  begun  in  1903  and  finished  in  1904. 
The  geological  work  has  been  carried  on  under  the  immediav 
direction  of  the  writer,  who  has  devoted  his  attention  particularj 
to  the  study  of  the  ore  deposits.  The  exceptionally  arduous  lab« 
of  discriminating  and  mapping  the  geological  formations  over  thi 
rugged  and  for  the  most  part  densely  wooded  region  has  been  Ave] 
performed  by  Mr.  Frank  C.  Calkins,  who  was  assisted  during  th 
"Lindgren,  W.,  Metasoniatic  processes  in  fissure  veins  :  Trans.  Am.  Inst.  Min.  En? 
vol.  30,  1901,  pp.  680-682.  Also  A  geological  reconnaissance  across  the  Bitteiroc 
Range  and  Clearwater  Mountains  in  Montana  and  Idaho:  Prof.  Paper  U.  S.  Geol.  Su 
vey  No..  27,  1904,  pp.  108-111. 
"Finlay,  J.  R.,  The  mining  industry  of  the  Coeur  d'Alenes,  Idaho:  Trans.  Am.  Ins 
Min.  Eng.,  vol.  33,  1903,  pp.'  235-271. 
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