COAL   ON   SOUTHWEST   SIDE   OF   BIGHORN    BASIN,    WYO.  213 
bed  whichhasbeenprospectedatthepointmarkedNo.21onPl.XI.  It 
continues  southeastward  for  about  2§  miles,  then  becomes  too  thin  to 
be  mined.  The  coal  is  subbituminous  and  suitable  for  domestic  pur- 
poses, but  the  bed  is  included  in  soft  shale,  which  renders  mining  diffi- 
cult. The  upper  Buffalo  Basin  to  the  south  is  encircled  by  an  out- 
crop of  the  Eagle  sandstone,  but  at  this  place  the  formation  does  not 
contain  workable  coal  beds.  West  of  this  basin,  near  the  Iron  Creek 
road,  the  Laramie  (?)  contains  two  beds  of  workable  coal,  one  near 
the  base  of  a  steep  northward-facing  bluff  and  the  other  near  its  sum- 
mit. A  section  measured  at  this  point  is  shown  in  No.  22,  PI.  XI. 
At  present  this  region  is  difficult  of  access,  but  with  increased  demand 
for  coal  small  mines  could  be  operated. 
The  western  part  of  the  district  contains  extensive  exposures  of  the 
Eagle  sandstone  which  are  coal  bearing.  A  bed  of  workable  coal 
extends  along  a  steep  westward-facing  scarp  on  the  east  side  of  Wood 
River.  The  bed  has  been  prospected,  but  no  attempt  at  mining  has 
been  made.  The  Sunshine  syncline  previously  discussed  is  encom- 
passed by  an  outcrop  of  coal-bearing  beds.  In  the  southern  half  the 
beds  attain  workable  thicknesses.  The  structure  is  unsymmetrical, 
the  east  limb  dipping  40°  to  50°  and  the  west  limb  10°  to  15°.  The 
trough  is  relatively  narrow  and  the  coal  beds  probably  do  not  pass 
below  workable  depths.  The  coal  occurs  in  two  beds  about  70  feet 
apart,  only  the  lower  one  being  of  minable  thickness.  The  thicker 
bed  ranges  from  less  than  30  inches  in  the  north  end  of  the  syncline 
to  7  £  feet  at  one  point  near  the  south  end.  Sections  measured  at 
intervals  about  the  syncline  are  shown  in  Nos.  28  to  35  on  PI.  XL 
The  coal  has  a  bright  luster,  is  medium  in  hardness,  and  is  relatively 
free  from  impurities.  A  mine  has  been  opened  in  Sunshine  Gulch 
and  a  small  amount  of  coal  taken  out. 
The  Sunshine  syncline  is  one  of  the  best  undeveloped  areas  in  the 
western  part  of  the  Bighorn  Basin.  It  contains  a  large  tonnage  of  coal 
in  a  favorable  attitude  and  of  a  quality  which  finds  ready  sale  in  the 
general  market. 
GRASS    CREEK    FIELD. 
The  Grass  Creek  field  lies  along  the  valley  of  Grass  Creek,  extend- 
ing from  Ilo  post-office  westward  to  the  foot  of  the  mountains  and 
from  Gooseberry  Creek  on  the  north  to  Cottonwood  on  the  south. 
There  are  two  coal-bearing  formations  the  Eagle,  which  i-  exposed 
in  a  zone  encircling  the  Grass  Creek  anticline,  and  the  Fort  I  oion. 
The  Eagle  coal  is  workable  along  the  northeast  side  of  the  am  iclineand 
at  intervals  on  the  west  and  southwest.  It  has  been  mined  at  Dickie 
No.  1  and  prospected  at  Dickie  No.  2  mine. 
A  bed  of  coal  of  workable  thickness  occurs  on  Kelt  Hand  Creek  in 
T.  46  N.,  R.  100  W.,  hut  owing  to  the  absence  of  good  land  sun  eys  in 
