LIMESTONE  AND  DOLOMITE,   BIRMINGHAM  DISTRICT,  ALABAMA.       249 
In  this  quarry  nearly  the  full  face  of  the  outcrop  on  the  valley  wall 
is  quarried,  the  stone  being  used  for  flux.  The  beds  dip  into  the  hill 
at  an  angle  of  15°.  The  limestone  has  been  extensively  quarried 
along  this  outcrop  for  some  distance  north  of  Dale,  though  all  the 
workings  except  that  at  Dale  have  been  abandoned.  These  aban- 
doned workings  suggest  that  the  quarrymen  continued  operations  to  a 
point  where  it  became  necessary  to  remove  too  much  cover  and  then 
moved  to  a  new  location.  Below  are  analyses  of  the  limestone  in  this 
locality : 
Analyses  of  Bangor  limestone  from  Compton  quarry,  north  of  Dale. a 
1. 
2. 
3. 
lilica  (Si02) 
2.05 
.76 
89.  64 
8.15 
4.  45 
3.  30 
86.  35 
2.  so 
.70 
04.  59 
Magnesium  carbonate  (MgCOs) 
n  Eckel,  E.  C,  loc.  cit. 
I.    \ ventre  sample  of  150  feel  of  rock  used  as  Mux.     .1.  L.  Beeson,  analyst. 
2  and  3.  Stockhouse  samples.     W.  B.  Phillips,  analyst. 
These  analyses  show  considerably  more  silica  and  magnesia  in  the 
limestone  in  this  locality  than  at  Blount  Springs.  Analysis  No.  2, 
however,  is  the  only  one  that  shows  an  injurious  amount  of  silica  with 
a  corresponding  low  percentage  of  lime  carbonate. 
The  limestone  outcropping  around  the  south  end  of  Blount  Moun- 
tain and  on  Canoe  Creek  has  never  been  utilized.  The  formation  is 
exposed  high  up  on  the  west  face  of  the  mountain  east  of  Village 
Springs,  where  it  must  reach  a  thickness  of  300  feet.  The  outcrop 
along  the  west  side  of  Birmingham  Valley  has  been  traced  southward 
to  Sayreton  Gap,  near  North  Birmingham.  The  limestone  thins 
toward  the  south,  being  at  Boyles  Gap  50  to  100  feet  thick  and  at 
Sayreton  Gap  only  a  few  feet.  South  of  Sayreton  Gap  it  has  not  been 
identified.  In  Shades  Valley  but  little  can  be  discovered  of  this  lime- 
stone. The  top  of  the  formation  outcrops  just  south  of  Trussville, 
where  it  has  been  quarried.  Between  Trussville  and  Argo  is  another 
small  showing.  Limestone  is  reported  in  wells  at  Trussville  at  a  depth 
of  12  feet.  Along  Shades  Valley  south  of  Irondale  only  chert  and 
shale  were  observed  in  outcrop,  and  although  thin  beds  and  lenses  of 
limestone  are  known  to  occur  in  the  generally  sandy  material  of  this 
part  of  the  valley,  the  deposits  can  have  no  economic  importance.  A 
considerable  thickness  of  chert  shows  along  the  valley  south  of  Truss- 
ville, and  it  is  probable  that  the  Bangor  limestone  has  been  more  or 
less  replaced  by  shale  and  other  siliceous  matter  along  this  belt,  a 
change  that  becomes  complete  farther  to  the  southeast  in  the  Cahaba 
Valley,  east  of  Leeds,  where  the  limestone  is  practically  absent,  having 
been  entirety  replaced  by  shale. 
