L42  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY.   L906,   PART    I. 
The  two  following  sections,   made  within  the  next   5  miles  to  (h 
southwest,  show   that  although  the  total  thickness  of  the  iron-bearing 
strata  in  this  direction  grows  gradually  less,  vet  the  thickness  of  work 
able  material  remains  fairly  constant. 
Character  of  Big  and  Trondale  seams  //<<//■  Lah    View,  Birmingham. 
Thickness; 
Character. 
Sandstone,  thin  bedded. 
Big  son  in : 
i  »re,  mined. 
Shale 
( >re,  not  mined 
Shale 
l  rondale  seam 
(  I  IV.  . 
Shale 
Ore.  - 
Ft.  in. 
{Soil  ore:  Metallic  iron,  im  percent;  insolul 
.';:»  ■  per  cent :  lime,  trace.  Hard  ore:  Meta 
iron,  XI:  percent;  insoluble,  26±  percent ;  Hi 
jo     percent. 
[Value  decreases  regularly  downward.    Soft,  c 
(t    '     Metallic  iron,  15  to  25  per  cent;  insoluble,  5C 
(i 
60  per  cent. 
.,    o  [Hard  ore:  Metallic  iron,  38d    per  cent;  insoli 
""     ;,  I      I6d      per   cent:   lime   carhonate,    2\±    per   ' 
•'  \        v'.n    .......     M  ..i  ..  n;..  ,-.....      i-   i      i.     : 
■J    2 
Soft  ore'  Metallic  iron,  (7  |    percent;  msolub 
26     percent.    Only  hard  ore  mined  al  presei 
Character  of  Big  ami  Trondah  seams  near  Lone  Pirn  <-n/>. 
Strata. 
Shale. 
(  uv,  mined 
Shale 
Ore,  not  mined 
Shale 
1  rondale  seam: 
ore.  net  mined . 
Thickness. 
/■'/.  in. 
[0  o 
1+ 
(.  6 
_'  o 
' 'ha  racier. 
[lard  ore:  Metallic  iron,  36d    percent;  insolubfl 
pci   cent .  lime  carbonate,  20       per  cent 
S<  ii  ore:  Met  iilic  iron,  1 1      |  er  cent ;  insolubl 
!  er  cent.    Semiha rd  ore  mined  at  presenj 
1 1  >eteriorates  in  value  regularlj   dovi  nward, 
l     ore  being  poorer  than  i hi  mit  mined  abo> e. 
Low  -grade  ore  interbedded  with  shale. 
'Idie  following  section  illustrates  the  complete  deterioration  of  1  lie 
'ronditle  seam : 
Character  of  Big  and  Irondah  seams  at  open  cut,  Greenspring  mine,  SW.  [sec.  ii.  T.  9  A'., 
/,'.  3  W. 
l! 
Sandstone,  coarse,  ferruginous. 
Shale,  yellow. 
Big  seam : 
Ore,    massive,    cross-bedded    and 
jointed;  mined. 
1'ai  I  ing  on  bedding  plane. 
ore.  rat  her  a  ferruginous  sandstone 
or  coarse  grit;    mined    in   only  a 
few  places. 
Shale 
Sandstone,  ferruginous  and  shaly 
Shale,  sandy 
Sand  stone,  ferrugin  ou  s 
Thickness. 
Ft.  in. 
Character. 
2 
1     0 
0 
l    3 
(Soft    ore:   Metallic  iron,    12  '     per  cent;   insoln 
;:i      percent :  lime.  2  •    per  cent.    Semihard  i 
Metallic  iron.  :<s  :     percent;   insoluble,  32d 
cent:   lime,  8       percent.     Mostlj    semihard 
I     nuned  at  present. 
. 
