ORE  DEPOSITS  OF  THE  NORTHERN  BLACK  HILLS. 
By  J.  D.  Irving. 
INTRODUCTION. 
In  the  several  steps  of  its  growth,  mining-  in  the  Black  Hills  has 
followed  closely  the  lines  of  its  development  in  other  regions.  First 
the  attention  of  the  early  prospectors  and  those  who  followed  them 
was  given  to  the  more  easily  accessible  deposits — the  placers.  As 
the  value  of  these  became  evident,  search  was  made  for  the  source 
from  which  the  gold  in  the  placers  was  derived.  The  old  gravel 
i  deposits  which  lie  at  the  base  of  the  Cambrian  series  were  then 
found,  and  for  a  number  of  years  yielded  very  good  returns  to  those 
who  had  located  on  them.  The  impregnated  lodes  in  the  schistose 
rocks  were  then  discovered,  and  the  mines  which  have  now  become  the 
famous  Homestake  belt  were  gradually  developed.  The  lead-silver 
ores  mined  at  Carbonate  then  became  productive,  and  still  further 
search  revealed  the  beds  of  refractory  siliceous  ore  which  have  of  late 
years  become  of  such  very  great  importance;  then  the  Ragged  Top 
ores  were  found,  and  finally  a  variety  of  smaller  deposits  was  discov- 
ered. Areas  where  ore  bodies  were  easily  accessible  at  the  surface 
were  first  prospected,  and  the  development  of  the  more  remote  and 
more  deeply  buried  ores  slowly  followed. 
To  make  the  description  of  the  ore  deposits  clear,  the  general  geolog- 
ical character  of  the  Black  Hills  will  be  briefly  described,  and  then 
the  different  types  of  ore  bodies  will  be  separately  treated. 
GEOLOGY. 
Geologically,  the  Black  Hills  differ  in  some  respects  from  almost 
any  other  region  in  this  country.  Surrounded  on  all  sides  by  flat 
and  rather  barren  plains  whose  general  aspect  is  monotonous  and 
without  special  interest,  the  Black  Hills  rise  as  an  island,  presenting 
within  their  borders  geological  problems  of  great  variety  and  interest, 
diverse  types  of  ore  deposits,  and  studies  in  land  drainage.  From  the 
very  isolation  and  circumscribed  character  of  this  uplift  many  of  its 
problems  are  easily  grasped  and  understood,  and  are  without  the  usual 
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