PORTLAND    CEMENT    MATERIALS    IN    EASTERN    WYOMING.       241 
brown  iron  stains  1J  inches  in  diameter.  The  limestone  is  practi- 
cally on  edge  and  could  be  cheaply  quarried,  possibly  by  the  use  of 
steam  shovels,  although  considerable  blasting  would  probably  be 
necessary  with  increase  in  the  depth  of  the  quarry.  About  60  feet 
of  this  limestone  is  exposed,  but  it  is  probable  that  a  greater  thick- 
ness could  be  proved  by  test  pits  in  the  flat  to  the  west.  The  rock 
was  traced  for  a  distance  of  one-eighth  of  a  mile  on  this  same  hill, 
and  again  outcrops  across  a  small  brook  to  the  south.  The  highest 
point  of  the  exposure  is  about  100  feet  above  the  valley  and  unques- 
tionably there  is  sufficient  limestone  here  to  last  a  large  plant  many 
years.  The  following  analysis  by  Mr.  A.  J.  Phillips  is  that  of  a  sam- 
ple-taken across  60  feet  of  the  limestone. 
Analysis  of  Niobrara  limestone. 
Silica  (Si02) 6.  44 
Alumina  ( A1203) : 1.  4G 
Ferric  oxide  (Fe203) 2.  32 
Manganese  oxide  (MnO) 11 
Lime  (CaO) 45.  90 
Magnesia  (MgO) 2.  05 
Sulphuric  anhydride  (S03) 07 
Alkalies  (K20) G6 
Water  at  100°  C 55 
Water  above  100°  C 33 
Ignition  loss 39.  71 
100.  10 
This  is  a  good  limestone  for  cement  making,  although  the  percent- 
age of  silica  as  compared  with  that  of  the  combined  alumina  and 
ferric  oxide  is  low.  Magnesian  carbonate  is  not  particularly  high, 
while  sulphur,  the  alkalies,  and  silica  are  exceedingly  low. 
Minnelcalita  limestone. — A  little  over  one-half  mile  west  of  Brad- 
ley station  the  Minnekahta  limestone  (Carboniferous)  forms  a  promi- 
nent escarpment  and  bench  extending  parallel  to  the  front  of  the 
range.  It  can  be  readily  recognized  from  its  topographic  form,  and 
from  the  fact  that  it  is  underlain  and  overlain  by  red  beds.  The 
limestone  is  50  feet  thick.  In  the  escarpment  it  dips  S.  80°  E.  at  an 
angle  of  65°,  and  to  the  west,  on  the  bench  or  terrace,  it  becomes 
approximately  flat.  It  is  gray,  purplish,  or  white  in  color,  and  is 
mostly  fine  grained,  dense,  and  rather  hard.  Joints  are  common 
throughout  the  mass  and  these  would  be  of  considerable  advantage 
in  quarrying.  Its  situation  for  quarrying,  however,  is  unfortunate, 
since  either  the  overlying  red  shales,  which  mask  the  lower  portion 
of  the  clifT,  would  have  to  be  shot  off  before  the  limestone  could  be 
quarried,  or  the  quarry  would  have  to  be  located  upon  the  top  of  the 
bench  and  an  expensive  tramway  built  to  the  flat  below.  A  railroad 
to  the  base  of  the  cliff  would  probably  have  a  rather  steep  grade.    A 
