GYPSUM  DEPOSITS  OF  THE  LARAMIE  DISTRICT,  WYOMING. 
By  C.  E.  SlEBENTIIAL. 
Introduction. — The  gypsum  deposits  of  the  district  are  of  two  varieties — earthy  gypsum 
or  gypsite,  and  rock  gypsum.  The  mill  of  the  Consolidated  Plaster  Company,  at  Red 
Buttes,  making  both  plaster  of  Paris  and  cement  plaster,  uses  rock  gypsum  with  a  smaller 
amount  of  gypsite,  while  the  plant  of  the  Acme  Cement  Plaster  Company,  near  Laramie, 
works  the  gypsite  exclusively. 
OCCURRENCES  OF  ROCK  GYPSUM. 
Red  Mountain. — The  heaviest  developments  of  gypsum  rock  in  the  district  are  found 
along  the -foot  of  the  north  slope  of  Red  Mountain,  in  the  extreme  soul  Invest  corner  of  the 
Laramie  quadrangle,  in  T.  12  N.,  R.  76  W.,  just  north  of  the  Wyoming-Colorado  line. 
The  gypsum  measures  first  appear  from  beneath  the  Tertiary  near  the  middle  of  the  west 
side  of  sec.  7  and,  winding  in  and  out  around  the  foothills  of  Red  Mountain,  take  in  the 
main  an  east-west  line  through  sees.  8,  9,  and  10,  pass  out  at  the  northeast  corner  of  the 
latter,  bend  to  the  north,  swing  sharply  westward  through  the  middle  of  sec.  3,  and  turn 
northward  again  near  the  middle  of  sec.  I,  the  gypsum  here  becoming  too  thin  to  be  of 
importance.  The  base  of  the  gypsum  beds  throughout  this  region  is  marked  by  a  bed  of 
limestone  a  foot  or  more  in  thickness,  which  is  nearly  everywhere  crowded  with  fossils, 
mostly,  however,  individuals  of  a  few  species.  These  have  been  determined  to  be  of 
Upper  Carboniferous  age.  A  section  of  the  gypsum  measures,  showing  the  maximum 
development  in  this  vicinity,  is  as  follows,  taken  from  the  top  of  the  beds  on  the  north 
foot  of  Red  Mountain,  in,sec.  9,  down  to  the  fossil  bed. 
Section  of  gypsum  measures  at  tin  bas(  of  Red  Mountain,  on  the  north  side. 
Feet. 
Kcl  gypsum  rock,  nearly  pure (> 
Red  shale 'A5 
Gypsum 3 
Red  shale 10 
Gypsum 4 
Reddish  shale 55 
Banded  gypsiferous  rock  (limestone) 5 
Red  sandy  shale 88 
i  rj  psum,  massive 67 
Fossiliferous  limestone 1 
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The  heavy  gypsum  bed,  ranging  in  thickness  from  30  to  60  feet,  extends  nearly  the 
whole  length  of  the  outcrop  outlined  above.     The  distance  to  Red  Buttes,  the  nearest 
point  on  the  railway,  is  about  25  miles. 
Sportsman  Lake. — A  mile  east  of  this  lake,  near  the  middle  of  the  north  side  of  sec.  7, 
T.  13  N.,  R.  73  W.,  there  is  an  outcrop  of  gypsum.  A  small  test  pit  sunk  at  this  point 
developed  4  or  5  feet  of  pure  rock  gypsum,  but  whether  this  is  the  full  thickness  of  the 
bed  is  not  known.  A  curly,  laminated,  gypsiferous  limestone  crops  out  a  quarter  of  a  mile 
east  of  the  gypsum  and  dips  beneath  it.  This  limestone  is  traceable  as  a  slight  ridge, 
east  of  north,  to  and  beyond  Forelle,  passing  a  quarter  of  a  mile  east  of  Red  Buttes 
station. 
Red  Buttes. — A  mile  south  of  Red  Buttes  station  and  a  quarter  of  a  mile  east  of  the 
limestone  ridge  just  described  is  a  deposit  of  gypsum  which  has  been  worked  by  the  Consoli- 
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