MILES    CITY    COAL   FIELD,   MONTANA.  57 
Section  of  Dominy  lignite  bed  in  sec.  18,  T.  7  N.,  R.  53  E. 
Ft.    in. 
Lignite 8 
Bone 8 
Lignite .• 3    3 
Sand 3 
Lignite. 
Bottom  of  section  concealed. 
Total  lignite 3  11 
F    LIGNITE. 
The  highest  bed  in  the  field,  marked  F  on  the  map  and  section,  has 
been  so  generally  destroyed  by  fire  as  to  be  of  little  economic  value. 
The  only  place  where  it  was  found  in  an  unburned  condition  is  in 
sec.  10  T.  7  N.,  R.  50  E.  The  bed  evidently  contains  several  feet  of 
workable  lignite,  but  its  full  thickness  was  not  exposed.  The  total 
area  of  land  containing  the  bed  in  workable  condition  does  not  exceed 
5  or  6  acres. 
QUANTITY  OF  AVAILABLE  COAL. 
In  addition  to  the  five  coal  beds  whose  outcrops  have  been  mapped, 
there  are  many  others  that  show  in  the  badland  bluffs  of  this  field, 
but  only  a  relatively  small  proportion  of  the  coal  exposed  is  of  work- 
able thickness  and  quality.  The  valuable  coal  lands  are  confined  to 
small  areas  whose  boundaries  can  not  be  determined  closely  without 
thorough  prospecting.  The  writers  have  estimated  the  total  quantity 
of  workable  coal  in  the  areas  classified  as  coal  land  at  780,080,000 
tons,  which  is  approximately  equal  to  the  tonnage  of  a  bed  0.68  foot 
thick  covering  the  whole  field,  but  owing  to  the  extreme  variability 
of  the  coal  beds  the  limit  of  error  in  this  estimate  is  necessarily  high. 
The  figures  given  above  are  conservative  and  represent  the  coal 
which  actually  outcrops  in  workable  thickness  and  quality.  On 
taking  into  consideration  the  general  distribution  of  the  small  areas 
of  workable  coal  and  its  probable  occurrence  in  other  areas  where 
there  are  no  natural  exposures,  it  is  reasonable  to  assume  that  the 
total  quantity  of  coal  that  may  be  developed  by  prospecting  will  be 
considerably  more  than  the  above  estimate. 
CHARACTER  OF  THE  COAL. 
PHYSICAL    PROPERTIES. 
The  coals  of  the  upper  member  in  this  field  are  brownish  in  color 
and  those  of  the  lower  member  are  nearly  black,  but  all  give  a  brown 
streak  when  cut  or  scratched  and  make  a  brown  powder  when 
crushed.  The  weathered  outcrop  or  blossom  of  the  coals  of  either 
type  is  black.     In  general    the   upper  lignites  retain  their  original 
