350  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1906,  PART    I. 
thick,  and  are  worked  in  connection  with  the  overlying  Pleistocene 
clavs  at  the  quarry  of  Bruce  H.  Campbell.     The  section  measured  at 
this  quarry,  given  on  page  349,  shows  20  feet  of  workable  shales  over-l 
Lying  the  coal.     They  are  dark  brown  and  drab  in  color,  somewhat 
sandy  and  concretionary.     This  shale  is  mixed   with  the  overlying 
elav,  and  the  mixture  is  used  in  making  a  buff  or  red  building  brick,] 
the  color  depending  on  the  proportions  of  shale  and  clay  used.     Thel 
beds  worked  at  this  quarry  rise  abruptly  toward  the  west  at  a  rate 
that  carries  the  Mercer  horizon  over  the  tops  of  the  hills  to  the  west.j 
SOUTH    FORE    DISTRICT. 
Flint  cl'ii/.  A  hand  of  clay  that  occurs  in  the  Pottsville  formation 
in  the  South  Fork  districl  has  been  worked  at  points  south  of  the 
Pennsylvania  Railroad  from  South  Fork  westward,  beyond  Mineral 
Point,  and  also  al  a  few  places  north  of  the  railroad.  In  this  district 
this  clay  is  characterized  by  a  persistenl  flinty  streak.  This  clay  is 
presenl  in  the  hills  along  Conemaugh  River,  in  an  area  extending 
asfarwesl  as  a  pohrl  aboul  1  mile  easl  of  Conemaugh  station.  The 
outcrop  is  continuous,  excepl  where  the  local  dips  and  change  in 
direction  of  the  river  carry  it  below  drainage.  The  flinty  clay  may 
not  he  always  presenl  between  Mineral  Point  and  Conemaugh.  For 
example,  the  clay  observed  at  this  horizon  in  the  tunnel  of  the  old; 
Portage  Railroad  is  nol  particularly  flint}  incharacter.  FromMineral 
Point  t<»  South  Fork,  however,  the  flinty  character  is  persistent. 
This  Hint  day  is  now   worked  by  the  Garfield  Fire  Clay  Company] 
near  the   viaduct,  and   by  J.    II.   Wickes    and    the  South    Fork   Fire 
Brick  Company,   wesl    of  South    Fork.     The   following  section  was' 
measured  at  Mr.  Wickes's  mine: 
Sectio  clay  at  ./    //.   Wickes' s  mine,  South  /-'oil;. 
Ft.   In. 
1 1'-. ivy  sandstone  roof- 
Plastic  clay 3£ 
1-2 
Mini  clay r 
Sandstone. 
This  clay  is  also  worked  by  the  Page-Reigard  Mining  Company! 
near  Mineral  Point  and  at  South  Fork,  hut  in  July,  1904,  the  mine  at; 
South  Fork  was  shul  down.  It  is  reported  that  the  plastic  clay  is 
persistent,  hut  that  the  thickness  of  the  Hint  clay  is  variahle,  dwind- 
ling to  14  inches  in  a  uortheast-southwesl  /one.  A  specimen  of  this 
flint  clay  from  the  central  hand  of  the  bed  worked  near  the  viaduct 
some  years  ago  was  analyzed  by  T.  T.  Morrell,  of  Johnstown,  with  the 
following  results: 
