LIMESTONE  AND  DOLOMITE,  BIRMINGHAM  DISTRICT,  ALABAMA.       251 
situated  near  the  center  of  this  valley,  the  limestone  showing  on  all 
sides.  The  limestone  in  Cahaba  Valley  is  generally  dark  gray  and  it 
is  much  thicker  bedded,  especially  in  the  lower  part,  than  along  Bir- 
mingham Valley.  Its  thickness  is  difficult  to  determine  accurately 
on  account  of  probable  irregularities  of  dip,  but  it  may  be  as  much  as 
1,000  feet.  Its  dip  in  the  vicinity  of  Leeds  is  15°  to  20°  SE.,  and  about 
4  miles  south  of  Leeds  dips  of  50°  E.  were  noted. 
The  Chickamauga  limestone  has  been  quarried  at  Gate  City  by  the 
Sloss  Iron  Company  for  use  as  flux,  but  it  is  no  longer  used  in  this 
region  for  that  purpose  to  any  extent.  The  subjoined  analyses  show 
the  composition  of  the  limestone  at  this  quarry: 
Analyses  of  Chickamauga  limestone  at  Gate  City  quarry.0 
Silica  (Si02) 
Iron  oxide  (Fe20;j) 
Lime  carbonate  (Ca(  O3) 
5.  70 
1.87 
91.16 
3.30 
2.14 
91.33 
a  Eckel,  E.  C,  loc.  cit. 
1.  Average  sample  from  crusher.     Uenry  McCalley,  analyst . 
2.  Average  of  four  samples.    J.  W.  filler,  analyst. 
The  high  percentage  of  silica  shown  by  these  analyses  probably 
indicates  the  reason  why  the  use  of  this  limestone  as  flux  has  been 
discontinued.  Much  purer  rock  can  be  obtained  in  the  region,  as  is 
shown  on  page  253. 
This  limestone  is  used  for  lime  near  Chepultepec,  in  Murphree  Val- 
ley, by  the  Cheney  Marble  and  White  Lime  Company.  The  quarry 
is  situated  on  the  east  face  of  West  Red  Mountain,  where  the  situation 
is  favorable  for  working  the  rock.  Below  is  a  section  of  the  limestone 
exposed  in  this  quarry : 
Section  of  Chickamauga  limestone  at  Chepultepec  quarry. 
Feet. 
Dark-gray  crystalline  limestone 40 
Darker  crystalline  limestone 20 
Blue  limestone ". 5 
Gray  limestone 2 
Blue  limestone 5 
Shaly,  impure  limestone 6 
Dark  amorphous  (lithographic?)  limestone 2 
Gray  limestone 10 
90 
The  gray  limestone  at  the  top  is  the  chief  source  of  material  for  lime. 
At  the  time  the  works  were  visited  (September,  1905)  two  kilns  were 
in  operation,  each  producing  100  barrels  of  lime  daily. 
At  Leeds,  in  Cahaba  Valley,  a  large  plant  has  been  built  which  will 
use  the  Chickamauga  limestone,  quarried  near  the  works,  for  cement 
