INVESTIGATION  OF  IRON  AND  NONMETALLIFEROUS  ECONOMIC 
MINERALS. 
By  C.  W.  Hayes,  Geologist  in  Charge. 
The  investigation  of  the  nonmetalliferous  minerals  has  been  car-i 
ried  on  during  the  year  1904  as  heretofore,  chiefly  m  connection  with 
work  on  areal  geology.  The  selection  of  areas  for  mapping,  how- 
ever, is  made  largely  with  reference  to  the  occurrence  of  such  mineral, 
deposits,  so  that  the  economic  aspect  of  the  work  is  generally  the 
most  important  one.  There  is  scarcely  an  area  in  the  United  States 
the  size  of  a  Survey  quadrangle  which  does  not  contain  more  than 
one  important  mineral  of  this  class  in  commercial  quantity.  The 
wide  distribution  of  some  of  these  minerals,  such  as  coal,  clay,  lime- 
stone, etc.,  while  adding  vastly  to  the  aggregate  value  of  the  lands 
explored,  makes  their  investigation  slow  and  expensive.  They  can 
not  be  studied  in  detail  with  advantage  in  advance  of  topographic 
and  areal  geologic  mapping. 
IRON  ORE. 
In  view  of  the  dominant  influence  of  the  Lake  Superior  region  in 
the  iron  industry  and  the  active  prospecting  being  carried  on  in  the 
various  districts,  it  is  considered  essential  that  some  field  work 
should  be  done  there  each  season.  This  consists  in  the  correction 
and  amplification  of  maps  and  sections  as  better  data  become  avail- 
able. A  summary  report  on  the  iron  districts  of  the  region  is  in 
process  of  preparation.  This  will  not  only  summarize  the  economic 
geology  of  the  several  monographs  already  published,  but  will 
embody  such  new  information  as  has  been  obtained  concerning  the 
extent  and  relations  of  the  ore  deposits.  During  the  past  year  field 
work  has  been  done  by  Messrs.  Van  Hise,  Leith,  and  Seaman. 
During  the  year  a  further  examination  has  been  made  of  the 
iron-ore  deposits  of  the  Rocky  Mountain  and  Pacific  coast  States 
by  Mr.  Leith.  This  reconnaissance  has  been  directed  chiefly  to 
obtaining  a  general  view  of  the  deposits  in  question  for  the  purpose 
of  planning  detailed  work  on  several  of  the  districts  during  the 
coming  year. 
28 
