252         CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   L906,   PART    I. 
manufacture.  The  li  most  one  here  is  thick  bedded  and  dips  15°  to  2CS 
E.  As  it  outcrops  hut  little  above  drainage  level,  quarrying  opera- 
tions will  be  more  difficult  and  expensive  than  in  a  quarry  entirely 
above  drainage.  So  far  as  its  known  composition  indicates,  this  lime- 
stone is  everywhere  suitable  for  cement  manufacture. 
The  most  favorable  locality  for  quarrying  the  limestone  in  this 
region,  with  regard  to  natural  conditions,  is  at  the  south  end  of  Blount 
Mountain,  when1  it  lies  nearly  flat  and  forms  high  hills  such  as  Foster 
and  Butler  mountains.  From  500  to  700  feet  of  limestone  is  here 
available,  entirely  above  drainage  and  exposed  on  all  sides.  This 
locality  could  be  easily  reached  from  the  Louisville  and  Nashville 
Railroad  by  a  spin-  .">  miles  long,  leaving  the  main  track  2  miles  north 
of  Mount  PinsoD  and  extending  up  Dry  ('reek  to  Foster  Mountain. 
KNOX   DOLOMITE. 
The  lower  .")()()  to  600  feet  of  t  he  Knox  dolomite,  which  is  i'vov  from 
the  chert  characterizing  the  upper  2,500  feet  of  the  format  ion.  is  largely 
used  as  (lux  in  the  furnaces  of  the  district.  This  chert-free  dolomite 
is  limited  below  by  the  thin-bedded,  bluish  to  dark-gray  Cambrian 
limestone  known  as  the  Conasauga  limestone. 
The  dolomite  outcrops  along  the  east  side  of  Opossum  Valley,  being 
quarried  by  the  Tennessee  Republic  Company  at  Thomas  and  by  the 
Sloss  Imn  Company  at  North  Birmingham.  The  outcrop  in  Opossum 
Valley  continues  as  a  narrow  belt  up  the  west  side  of  Birmingham 
Valley  to  Mount  Pinson.  Along  the  east  side  of  Birmingham  Valley 
t  he  outcrop  extends  in  a  narrow  belt  to  a  point  within  I  mile  of  Chalk- 
ville.  Besides  the  quarries  mentioned  above,  the  Spencer  quarry  of 
the  Lacy-Buck  lion  Company  at  Lardona  and  that  of  the  Tennessee 
Republic  Company  at  Ketona.  as  well  as  the  old  quarry  at  Dolcito, 
are  located  along  the  western  belt.  The  eastern  and  western  belts  of 
outcrop  are  connected  between  North  Birmingham  and  East  Birming- 
ham, where  the  dolomite  lies  nearly  flat  and  makes  a  wide  outcrop 
separating  the  chert  ridge  in  Birmingham,  known  as  Cemetery  Ridge, 
from  the  chert  ridge  extending  northeastward  from  East  Birmingham 
to  Blount  Mountain.  There  is  an  outcrop  of  the  dolomite  in  Murphree 
Valley  extending  along  the  east  side  of  Gravelly  Ridge  from  Chepul- 
tepec  to  Remlap.  It  is  well  exposed  on  Blackburn  Fork  west  of 
Swansea,  as  a  bluff  about  100  feet  high.  The  dolomite  is  also  known 
to  occiii'  along  the  east  side  of  the  Cahaba  trough,  at  the  west  base  of 
Pine  Mountain,  where,  on  account  of  its  vertical  attitude,  ils  outcrop 
is  narrow,  though  it  probably  extends  for  10  miles  diagonally  across 
the  southeast  corner  of  the  Birmingham  quadrangle. 
The  dolomite  is  generally  gray  in  color  and  more  or  less  crystalline 
in  texture.  As  shown  by  the  accompanying  analyses,  it  is  nearly  i'wv 
from  silica,  though  thin  plates  of  chert  or  silica  in  some  other  form  are 
