emmons.]  INVESTIGATION    OF    METALLIFEROUS    ORES.  23 
IDAHO. 
A  special  examination  of  the  Coeur  d'Alene  mining  district  of  Idaho 
is  in  progress.  The  area  to  be  surveyed  covers  two  15-minute  sheets, 
or  one-eighth  of  a  square  degree.  Mr.  Calkins  has  been  occupied 
during  the  summer  on  the  areal  geology  of  the  region — that  is,  the 
geological  mapping.  This  work  was  not  completed  before  the  field 
season  was  closed  by  snow.  Completion  of  the  areal  geology  and 
investigation  of  the  ore  deposits  will  be  carried  on  during  the  coming 
season.     No  preliminary  report  is  made. 
INDIAN    TERRITORY. 
Reported  Gold  Deposits  of  the  Wichita  Mountains,  by  H.  Foster  Bain. 
This  presents  the  results  of  an  examination  of  the  mines  and  pros- 
pects of  the  district,  made  for  the  purpose  of  determining  whether  the 
land  is  mineral  land  under  the  Government  definition.  The  most 
promising  and  important  prospects  were  visited  and  their  ores  care- 
fully sampled.  These  were  then  assayed  in  the  laboratory  of  the  Sur- 
vey, with  the  result  that  no  trace  of  gold  was  found  in  any  of  the 
samples,  and  in  only  one  or  two  cases  was  a  small  percentage  of  cop- 
per or  lead  found. 
ILLINOIS. 
Lead  and  Zinc  Deposits  of  Illinois,  by  H.  Foster  Bain. 
This  is  a  review  of  the  present  condition  of  the  mining  industry  of 
these  two  metals  in  the  State  of  Illinois,  the  main  production  at  pres- 
ent being  from  zinc  ores,  mostly  sulphides,  in  the  northwestern  part 
of  the  State. 
NEVADA. 
Economic  Geology  of  the  Silver  Peak  Quadrangle,  by  J.  E.  Spurr. 
During  the  past  summer  Mr.  Spurr  made  an  examination  of  the  ore 
deposits  of  the  Silver  Peak  quadrangle,  an  area  lying  southwest  of 
Tonopah,  along  the  Nevada-California  boundary.  In  this  area  mining 
has  been  carried  on  very  intermittently  since  186-1.  It  contains  a  large 
amount  of  low-grade  ores,  carrying  values  in  gold  and  silver.  Litiga- 
tion has  been  one  of  the  causes  which  have  retarded  its  development. 
Another  probable  cause  may  be  found  in  the  rather  unusual  character 
of  the  deposits  from  a  geological  standpoint.  They  are  not  true  veins 
in  the  ordinary  sense  of  the  word.  The  most  important  quartz  bodies, 
according  to  Mr.  Spurr,  are  offshoots  from  a  very  siliceous  granite; 
others  are  contact  deposits  in  limestone  around  the  peripheiy  of  the 
granite  bodies.  In  either  case  it  is  difficult  to  foretell  their  probable 
extent  in  depth.  The  extremely  arid  character  of  the  region  is,  more- 
over, a  serious  obstacle  to  cheap  exploitation.     The  intelligence  and 
