22  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1900,  PART    I. 
6.  Brown  hematites  (" gossan  ores")  of  Carroll  and  Floyd  counties. 
During  1905  and  1906  detailed  field  work  was  done  on  the  ores 
of  classes  3  and  4;  the  ores  of  class  2  were  examined  in  less  detail 
at  several  localities  in  1905,  while  on  those  of  classes  1,  5,  and  6  no 
field  work  was  done.  It  is  planned  to  complete  the  work  during  1907 
by  examinations  of  the  ore  deposits  not  yet  visited. 
Pennsylvania -New  Jersey. — A.  C.  Spencer  has  for  some  time 
been  engaged  in  a  very  detailed  study  of  the  iron,  zinc,  and  man- 
ganese deposits  of  the  Franklin  Furnace4  district  of  New  Jersey.  Tn 
connection  with  this  work  he  examined  a  number  of  magnetite 
deposits  elsewhere  in  New  Jersey  and  in  New  York,  and  has  formu- 
lated theories  of  occurrence  and  origin  which  seem  to  have  an  impor- 
tant bearing  on  the  future  development  of  these  ores.  The  explora- 
tory work  so  far  done  by  mining  companies  has  been  of  a  rather 
haphazard  nature,  based  on  no  definite  working  theory.  It  is  hoped 
that  the  publication  of  Mr.  Spencer's  report  will  supply  the  pros- 
pector and  miner  with  data  which  will  serve  asa  guide  both  in  locatinj 
and  valuing  t  he  deposits. 
At  the  close  of  work  in  the  New  Jersey  area  Mi-.  Spencer  took  up 
the  study  of  the  important  and  extensive  magnetite  deposits  which 
occur  near  the  Triassic  border  in  southwestern  Pennsylvania.  An 
introductory  report  on  these  magnetites  of  the  Cornwall  type  is 
included  in  the   presenl    bulletin. 
Western  States. — Two  distinct  ('adds  of  work  have  been  entered 
upon  by  the  Survey  in  its  investigation  of  western  iron  ores.  S.  II. 
Ball  spent  most  of  the  held  season  of  L906  in  examining  and  map] 
ping  the  important  Ilartville  iron-ore  district  of  Wyoming.  A 
brief  preliminary  report  on  the  results  of  this  work  is  included  in  the 
present  bulletin,  and  a  special  bulletin  on  the  subject  will  be  pub- 
lished by  the  Survey  during  1907.  At  the  close  of  this  work  Mr.  Ball 
made  brief  examination  of  the  titaniferous  iron  ores  of  Iron  Moun- 
tain, Wyoming,  a  report  on  which  is  presented  later  in  this  bulletin] 
In  Utah  C.  K.  Leith  and  assistants  carried  out  very  detailed 
mapping  of  important  iron  deposits,  and  the  Survey  will  probably 
publish  the  results  of  this  work  in  a  separate  bulletin  during  1907. 
MANGANESE. 
As  most  of  the  manganese  ores  of  the  United  States  are  closely 
associated,  both  geographically  and  geologically,  with  brown  iron 
ores,  work  on  the  two  products  is  best  carried  on  by  the  same  Survey 
parties.  In  the  course  of  the  work  on  the  southern  iron  ores  out- 
lined on  a  previous  page  considerable  data  have  been  collected  con- 
cerning the  manganese  ores  of  Virginia,  Georgia,  and  Alabama. 
The  prosperity  of  the  steel  industry  has  greatly  stimulated  interest 
in  the  subject  of  manganese  ore  deposits,  and  a   marked   revival  of 
