CLAYS    OF    WESTERN    KENTUCKY    AND    TENNESSEE.         421 
A  small  amount  of  the  clay  is  shipped  to  the  Union  City  Tile  Company  at  Union  City, 
Tenn.,  where  it  is  mixed  with  common  surface  clay  for  making  drain  tile. 
Nos.  15  and  16;  Columbus,  Hickman  County. — These  clays  came  from  the  bluff  above 
Columbus,  65  feet  above  low  water.  They  are  highly  siliceous,  containing  85.18  per  cent  of 
silica  and  10.26  per  cent  of  alumina.     The  plasticity  is  due  to  the  fine  division  of  the  silica. 
One  mile  up  the  river  from  Columbus,  at  the  point  where  the  river  leaves  the  bluff,  is  a 
lens  of  chocolate-colored  plastic  clay  containing  numerous  leaf  impressions  and  fragments 
of  lignite.  The  clay  is  embedded  in  the  coarse  sand  which  outcrops  along  the  bluff  from 
this  point  to  Columbus.     It  is  used  at  the  Rucker  stoneware  plant  at  Columbus. 
No.  19-28;  Hickman,  Fulton  County.— The  bluff  at  Hickman  rises  about  180  to  200  feet 
above  the  river  and  contains  about  105  to  115  feet  of  greenish  joint  clay  and  clay  stone. 
This  is  overlain  by  10  to  20  feet  of  Lafayette  sand  and  gravel,  and  this  in  turn  by  65  to  70 
feet  of  loess. 
The  clays  vary  from  a  highly  siliceous  clay  stone  to  a  plastic  joint  clay.  Clays  Nos.  19, 
20,  22,  and  23  are  quite  refractory  before  the  blowpipe. 
The  clays  were  analyzed  by  Dr.  A.  M.  Peter,«  who  says: 
It  is  quite  evident  that  the  Tertiary  bluffs  from  which  these  clays  were  collected  offei  some  valuable 
materials  to  the  industrial  arts.  Some  of  these  are  quite  refractory,  especially  Nos.  19,  20,  22,  and  23  [of 
this  report],  and  would  probably  make  good  fire  bricks,  etc.  Others  could  be  employed  for  terra-cotta 
work  and  other  forms  of  pottery,  while  some  of  these  abundant  deposits  might,  no  doubt,  be  used  with 
advantage  in  mixture  with  the  more  calcareous  soft  material  found  in  some  of  these  beds  in  the  manu- 
facture of  hydraulic  cement  of  the  character  of  the  celebrated  Portland  cement. 
None  of  the  Hickman  clays  are  being  worked. 
Pryorsburg,  Graves  County. — The  largest  output  of  clay  from  any  of  the  Kentucky 
deposits  comes  from  the  Kentucky  Construction  and  Improvement  Company's  pit,  1  mile, 
north  of  Pryorsburg.  The  clay  was  first  discovered  in  a  small  outcrop  on  the  north  side  of  a 
small  hill  near  the  main  line  of  the  Illinois  Central  Railroad.  A  bed  20  feet  thick  and  with  a 
strong  dip  to  the  south  is  now  being  worked  by  open  pit  and  tunnel.  Holes  have  been  bored 
into  the  clay  to  a  depth  of  100  feet  without  penetrating  the  deposit. 
The  clays  consist  of  fine  white  ball  and  sagger  clays  used  for  making  chinaware,  insula- 
tors, and  decorated  tile.  A  large  per  cent  of  the  output  is  shipped  to  East  Liverpool,  Ohio. 
Mr.  M.  B.  Cooley  is  general  superintendent. 
Rock,  Graves  County. — A  small  stoneware  plant  is  located  at  Rock,  in  the  southeast  corner 
of  Graves  County.     Only  the  common  ware,  such  as  jugs  and  churns,  is  made  here. 
The  clay  used  at  this  plant  comes  from  a  pit  near  the  former  post-office.  These  beds 
occur  in  lenses  about  100  feet  long,  40  to  50  feet  wide,  and  2  to  15  feet  thick.  There  are  usu- 
ally a  large  number  of  lenses  near  together.  The  clay  is  very  low  in  silica  and  high  in  alu- 
mina, and  burns  to  a  white-cream  color.  The  ware  is  burned  in  updiaft  kilns.  The  owners 
of  the  plant  are  W.  B.  Howard  &  Sons. 
PORTERS  CREEK  CLAY. 
In  Kentucky  and  the  larger  part  of  Tennessee  the  Porters  Creek  clay,  commonly  called 
"soapstone, "  forms  the  lowest  visible  member  of  the  Tertiary.  It  consists  of  a  black,  stiff 
joint  clay,  containing  a  large  amount  of  fine  sand  and  mica.  Tt  carries  a  high  per  cent  of 
iron  and  burns  to  a  pink  color.     In  speaking  of  this  clay  Dr.  R.  H.  Loughridge&  says: 
Tests  made  at  the  Rookwood  Pottery  indicate  that  it  can  not  be  used  for  glazed  ware  because  of  the 
shivering  of  the  glaze.  It  might  be  successfully  used  in  the  manufacture  of  water  jars,  which  require  no 
glazing.  The  unglazed  biscuit  is  pink  in  color.  When  mixed  with  an  equal  weight  of  the  white 
plastic  clay  from  Russell's  pottery  (Pottertown)  east  of  Murray,  it  receives  a  good  glaze  and  makes 
a  light  chocolate-colored  ware,  dotted  with  black  specks  from  the  mica  particles. 
a  Jackson  Purchase  region:  Kentucky  Geol.  Survey,  p.  100. 
b  Op.  eit. 
