LEWISTOWN   COAIi  FIELD,   MONTANA. 
117 
cates  that  the  Kootenai  may  possibly  be  coal  bearing  beyond  the  ter- 
ritory represented  on  the  map,  and  the  extent  of  the  coal  bed  north 
from  the  outcrop  can  only  be  conjectured.  In  the  vicinity  of  Giltedge, 
however,  the  coal  thins;  hence  the  district  is  fairly  well  defined  in 
that  direction.  From  present  evidence  it  would  seem  that  the 
McDonald  Creek  district  includes  about  75  square  miles,  although  the 
coal  either  has  been  removed  by  erosion  or  is  too  deep  for  working  in 
a  considerable  part  of  that  area. 
In  the  McDonald  Creek  district,  as  elsewhere  in  the  Lewistown  coal 
field,  there  is  but  one  workable  bed,  which  occurs,  also  as  in  other 
parts  of  the  field,  in  close  association  with  and  immediately  under- 
lying the  massive  gray  or  pinkish  sandstone  in  the  lower  part  of  the 
Kootenai.  Below  this  workable  bed,  at  a  distance  ranging  from 
15  to  40  feet,  occurs  another  coal  bed,  which,  because  of  its  charac- 
teristic alternation  of  coal  and  bone  in  thin  layers,  is  locally  termed  the 
"  dirty  vein."  Above  the  main  bed  there  are  several  coaly  layers, 
at  least  in  the  eastern  portion  of  the  district,  where  seams  a  few  inches 
thick  were  noted  in  the  sandstone  overlying  the  workable  coal.  In 
the  vicinity  of  Giltedge  a  bed  just  beneath  the  second  sandstone  of 
the  Kootenai  has  been  prospected  in  several  localities,  but  nowhere 
has  coal  more  than  a  few  inches  thick  been  discovered.  This  bed  is 
about  90  feet  above  the  main  coal  bed. 
Though  much  of  the  McDonald  Creek  district  is  underlain  by  work- 
able coal,  the  thickness  of  the  bed  varies  to  such  a  degree  that  no 
representative  section  can  be  given.  In  all  the  mines  but  two,  the 
Peiper  and  the  Black  Diamond,  where  there  is  only  one  bed  without 
parting,  the  coal  is  in  two  distinct  benches.  For  the  purpose  of  com- 
parison, sections  from  a  number  of  localities  in  the  area  are  given 
below. 
Sections  of  coal  beds  in  McDonald  Creek  district. 
SPRING  CREEK  MINE. 
Shale,  gritty. 
Coal 
Bone 
Coal 
Coal,  bony 
Clay. 
RLACK    DIAMOND  MINK. 
Bone. 
Coal. 
Clay. 
Ft. 
in 
2 
2 
6 
10 
1 
4 
4 
10 
Ft. 
in. 
4 
4 
BREW  &  PARSON'S  MINE. 
Bone. 
Coal . . 
Shale. 
Coal.. 
Clay. 
HILL'S  MINE. 
Sandstone. 
Coal,  impure. 
Clay 
Coal 
Ft.  in. 
5 
3     2 
2     2 
2     6 
8     3 
Ft.    in. 
1  2 
! 
2  4 
3  6} 
Development.  —Development  in  the  McDonald  Creek  district    1ms 
been  both  tardy  and  desultory.     Coal  was  mined  on  Big  Spring  ( Jreek 
