320         CONTRIBUTIONS    TO   ECONOMIC    GEOLOGY,  1906,  PART    I. 
USES. 
The  choicest  of  the  clay  is  sold  for  glasshouse  use.  At  several  of 
the  mines  the  clay  is  assorted,  that  which  is  freest  from  impurities 
being  sold  in  the  raw  condition  for  glass  pots.  Good  clay  which  con- 
tains a  small  amount  of  impurity  is  washed  and  then  sold  for  the  same 
purpose.  For  brick  it  is  not  necessary  that  the  clay  be  so  pure. 
Much  of  the  fire  clay  mined  in  Cheltenham  is  used  without  assorting 
for  ornamental  and  facing  bricks  or  is  mixed  with  various  other  clays 
to  make  sewer  pipe. 
FIRE    (LAV    IN"    OTHER     LOCALITIES. 
About  «.)  miles  northwest  of  Cheltenham  and  3  miles  east  of  Creve 
Coeur  Lake  the  St.  Louis  Vitrified  and  Fire  Brick  Company  operates 
a  mine  and  factory.  The  base  of  the  fire  clay  bed  at  this  point  is 
nearly  !»<)  feel  below  the  upland  level.  The  thickness  of  the  clay  is  12 
to  15  feet.  L2  feet  of  good  clay  being  mined.  It  is  practically  certain 
that  this  clay  U  at  the  same  horizon  as  that  mined  in  the  city  of  St. 
Louis.  This  mine  is  within  one-half  mile  of  the  western  outcropping 
edge  of  the  coal  measures.  Beneath  the  cla\  is  a  sandstone  with  fer- 
ruginous nodules;  above  are  0  inches  of  slate  overlain  by  18  inches  of 
coal.  Above  that  are  55  feet  of  soft  shales,  mostly  of  a  red  color. 
Essenl  ially  t  he  same  sect  ion  was  noted  in  drilling  at  t  he  St .  Louis  Clay 
Burning  Company's  plant,  one-half  mile  to  the  southeast.  At  this 
place,  it  is  said,  lime-tone  was  encountered  beneath  the  clay.  There 
is  also  a  lire  clay  mine  at  Malcolm  station,  southeast  of  Creve  Coeur 
Lake.     The  sect  ion  there  is  the  same,  including  the  1.8-inch  coal  seam. 
Fire  clay  has  long  been  known  north  of  Baden,  a  northern  suburb 
of  St.  Louis.  At  the  -hale  quarry  of  the  St.  Louis  Portland  Cement 
Company  the  massive  shales,  which  are  mined,  are  underlain  by  from 
2  to  3  feet  of  black  -hale  and  this  by  1  '  feet  of  coal,  beneath  which 
is  the  lire  clay. 
In  view  of  the  wide  separation  of  the  points  at  which  the  Chelten- 
ham (ire  clay  scam  j^  mined,  it  is  quite  probable  that  it  may  be  found 
at  many  places  where  no  prospecting  has  yet  been  done. 
SHALES. 
A  characteristic  feature  of  the  coal  measures  near  St.  Louis  is  its 
very  large  proportion  of  plastic  shales.  These  are  largely  used  in 
the  manufacture  of  vitrified  paving  brick,  both  in  St.  Louis  and  at 
points  farther  northwest,  near  Creve  Coeur  Lake.  This  shale  is  that 
which  appears  in  the  sections  above  the  fire  clay,  but%est  and  north 
of  the  city  it  occurs  in  thicker  and  more  continuous  beds,  of  uniform 
quality.  At  Castello  and  Malcolm  stations  almost  the  entire  40  to 
55  feet  intervening  between  the  loess  and  the  coal  seam  overlying 
