CLAYS    AND    SHALES    IN    CLARION    COUNTY,  PA.  339 
sand,  and  has  a  chalky  appearance  due  to  weathering,  while  the  lower 
part  is  harder  and  rather  sandy  and  is  greenish  in  color.  The  softer  and 
more  plastic  portion  of  the  bed  is  used  as  it  comes  from  the  bank  in  the 
manufacture  of  small  pieces,  but  the  hard  portion  is  washed  free  from 
sand  and  used  for  large  ware.  At  the  time  of  the  writer's  visit  the  clay 
below  the  Lower  Kittanning  coal  had  been  used  experimentally,  but  no 
definite  results  had  been  obtained.  The  Middle  Kittanning  clay  was 
formerly  stripped  on  Town  Run,  opposite  the  opening  of  the  No.  2 
mine  of  the  Alcola  Coal  Company.  The  quality  of  the  clay  here  is 
reported  to  be  excellent  for  pottery  manufacture. 
Freeport  horizons. — Plastic  clay  occurs  below  each  of  the  Freeport 
coals,  but  beds  at  these  horizons  are  comparatively  limited  in  area 
and  few  good  opportunities  were  offered  for  measuring  sections. 
The  best  section  noted  was  in  a  country  bank  just  west  of  Hickory 
Ridge  schoolhouse,  where  3  feet  were  exposed  below  the  coal. 
FLINT  CLAYS. 
Mercer  horizon. — No  good  exposure  of  flint  clay  was  seen  at  this 
horizon  within  the  quadrangle.  Just  south  of  it,  however,  at  Climax 
and  St.  Charles,  flint  clay  from  this  horizon  is  used  in  making  high- 
grade  fire  brick. a  At  one  point  within  the  quadrangle — viz,  on  the 
west  side  of  Leatherwood  Run,  about  1  mile  north  of  St.  Charles — 
fragments  of  flint  clay,  which  are  probably  from  this  horizon,  have 
been  found  in  a  field,  but  several  prospect  holes  sunk  here  failed  to 
find  the  source  of  the  fragments. 
Lower  Kittanning  horizon. — Flint  clay  occurs  below  the  Lower  Kit- 
tanning coal  in  a  belt  that  extends  across  the  north  half  of  the  quad- 
rangle with  a  width  of  1J  to  2^  miles  on  each  side  of  Clarion  River, 
except  in  an  area  north  of  Clarion.  Owing  to  the  height  of  the  clay 
in  the  hills,  however,  only  a  relatively  small  portion  of  the  area  is 
actually  underlaid  by  it.  The  clay  is  persistent  in  its  occurrence, 
but  varies  greatly  in  quality.  It  has  been  used  to  considerable 
extent,  so  its  qualities  are  fairly  well  known.  The  best  clay  is 
light  yellowish  brown  in  color,  fine  grained  in  texture,  and  moderately 
hard.  Weathered  pieces  are  bluish  gray  on  exposed  surfaces  and  are 
easily  broken.  The  following  chemical  analyses,  made  by  P.  H. 
Bates,  of  the  United  States  Geological  Survey's  laboratories  for  test- 
ing structural  materials,  at  St.  Louis,  Mo.,  indicate  the  quality  of  an 
average  sample  of  this  clay. 
a  Bull.  U.  S.  Geol.  Survey  No.  279,  p.  162. 
