THE  BENTONITE  DEPOSITS  OF  WYOMING. 
By  C.  A.  Fisher. 
Introduction. — The  variety  of  clay  known  as  bentonite  was  first 
described  in  1898  by  the  late  Prof.  W.  C.  Knight,05  of  the  Wyoming 
State  School  of  Mines.  The  first  name  given  to  this  product  was 
taylorite,  in  honor  of  Mr.  William  Taylor,  of  Rock  Creek,  Wyo.,  who 
brought  the  clay  to  notice.  It  was  discovered  later,  by  Mr.  Knight, 
that  the  name  taylorite  was  preoccupied,  consequently  bentonite h 
was  proposed,  after  the  Benton  formation,  in  which  the  most  exten- 
sive deposits  of  this  peculiar  variety  of  clay  are  found.  This  forma- 
tion has  a  wide  distribution  throughout  the  Northwest,  particularly 
in  Wyoming.  The  deposits  in  the  northeastern  part  of  the  State,  in 
the  vicinity  of  Newcastle,  were  first  described  in  detail  by  Mr.  N.  H. 
Darton.c  During  the  last  season  the  writer  found  some  thick  de- 
posits in  the  northern  part  of  the  Bighorn  basin,  in  Bighorn  County, 
Wyo. 
Physical  properties. — Fresh  bentonite  usually  has  a  yellow  ish- 
green  color,  but  assumes  a  light  cream  tint  on  exposure.  It  is  a  fine- 
textured,  soft,  massive  variety  of  clay  which  is  unctuous  to  the  touch 
and  which,  on  the  addition  of  water,  forms  an  emulsion.  The  mate- 
rial is  characterized  by  its  unusual  absorbent  qualities,  having  the 
capacity  of  absorbing  three  times  its  weight  of  water.  In  a  com- 
parative test  it  is  reported  to  have  taken  up  twice  as  much  glycerin 
as  infusorial  earth.  When  fresh  from  the  quarry,  it  breaks  with 
conchoidal  fracture,  but  upon  exposure  loses  this  property  and 
crumbles  to  a  light  yellowish  powder  resembling  corn  meal.  It  was 
formerly  classed  with  fire  clays,  but  owing  to  its  fluxing  properties 
is  unfit  for  this  purpose.  / 
This  mineral  is  a  hydrous  silicate  of  alumina,  a  clay  possessing 
peculiar  physical  properties.  The  specific  gravity  of  this  clay,  when 
fresh,  is  2.18.  Its  resemblance  to  ehrenbergite  of  Germany  has  been 
pointed  out  by  Mr.  Knight.     The  composition  of  the  clay  from  dif- 
°  Eng.  and  Min.  .Tour.,  vol.  63,  pp.  600-001. 
bEng.  and  Min.  Jour.,  vol.  66,  p.  401. 
c  Darton,  N.  II.,  Geologic  Atlas  TJ.  S.,  folio  No.  107,  U.  S.  Geol.  Survey,  1904. 
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