bain.1  FLUORSPAK    DEPOSITS    OF    SOUTHERN    ILLINOIS.  507 
grades,  remembering-  always  that  at  any  increase  in  prices  it  becomes 
cheaper  to  use  less  efficient  fluxes.  It  follows  that  while  the  output  can 
be  increased,  prices  probably  can  not  be  much  changed. 
With  these  facts  in  mind  it  is  seen  that  the  fluorspar  mines  of  the 
Kentucky-Illinois  district  will  have  for  many  years  an  important  and 
growing  market  to  supply.  Their  only  competitors  are  the  importers, 
and  competition  with  them  is  mainly  a  matter  of  transportation  costs. 
Mines  in  the  Rocky  Mountain  region  and  other  Western  States  can 
not  be  expected  to  disturb  the  fluorspar  market.  Such  fluorspar  as 
occurs  in  connection  with  the  ores  of  that  region  will  probably  always 
have  a  sufficient  local  market.  The  quantity  present  is  not  important 
in  any  western  district  yet  described,  and  local  smelters  make  an 
allowance  for  lime  which,  entirely  aside  from  the  cost  of  transporta- 
tion, is  likely  to  prevent  shipments  of  spar  to  the  east. 
GEOLOGY  OF  THE  DISTRICT. 
General  statement. — The  geology  of  the  Kentucky  portion  of  the 
district  was  studied  in  1889  and  1890,  and  again  in  1902  by  Mr.  Ulrich. 
In  1903  the  Illinois  area  was  studied  by  the  writer,  in  cooperation  with 
Mr.  Ulrich  and  with  the  assistance  of  Mr.  A.  F.  Crider.  A  report  is 
now  in  preparation.  The  formations  on  the  two  sides  of  the  river  are 
equivalent,  except  that  in  Illinois  certain  lower  beds  come  to  the 
surface  and  there  is  apparently  a  slightly  greater  variety  in  the 
igneous  rocks. 
Sedimentary  deposits. — The  section  as  made  out  by  Mr.  Ulrich  from 
a  study  of  the  Kentucky  area,  consists  of  the  following  formations: 
At  the  top  is  the  coarse  sandstone  and  conglomerate  forming  the  base 
of  the  coal  measures  of  the  Pennsylvanian  series.  Next  below  it  are 
the  sandstones,  shales,  and  limestones,  together  forming  the  Chester 
group,  and  having  a  total  thickness  of  about  700  feet.  Underlying  the 
Chester  is  what  was  called  the  Princeton  limestone, a  but  to  which  the 
name  Ste.  Genevieve  is  now  applied.  This  is  200  to  250  feet  thick, 
the  lower  two-thirds  oolitic,  and  the  upper  somewhat  shaly.  It  in 
turn  rests  on  the  well-known  St.  Louis  limestone,  which,  in  the  area 
under  consideration,  is  very  commonly  cherty. 
In  the  northwestern  portion  of  Hardin  County,  111.,  there  is  a  small 
structural  dome  which  brings  up  beds  below  the  St.  Louis.  The  first 
to  appear  from  below  the  latter  is  a  siliceous  limestone,  somewhat  simi- 
lar in  general  appearance  to  the  St.  Louis,  but  gradually  changing 
toward  the  base  into  sandy  shales.  This  was  recognized  by  Mr.  Ulrich 
as  the  equivalent  of  the  Tullahoma  formation  of  central  Tennessee. 
It  occupies  the  position  in  the  general  section  filled  by  the  Keokuk, 
Burlington,  and  Kinderhook  formations,  farther  north.  Below  it  is  the 
black  shale  of  the  Chattanooga  formation,  the  well-known  Devonian 
a  Bull.  U.  S.  Geol.  Survey  No.  213,  1903,  p.  207. 
