CLAY  DEPOSITS  OF  THE  WESTERN  PART  OF 
THE  DCKANGO-GALLUP  COAL  FIELD  OF  COLO- 
RADO AND  NEW  MEXICO. 
By  Millard  K.  Shaler  and  James  11.  Gardner. 
INTRODUCTION. 
The  greater  pari  of  the  area  here  considered  lies  in  northwestern 
New  Mexico,  hut  a  portion  is  included  in  southwestern  Colorado.0  In 
connection  with  reconnaissance  work  done  in  1*906  in  this  coal  held, 
brief  notes  were  taken  regarding  the  occurrence  and  development  of 
clay  and  shale  deposits.  As  the  region  is  hut  sparsely  settled  and  at 
present  lacks  adequate  railway  facilities,  the  clay  industry  supplies 
only  local  demands  and  a  small  outside  market.  The  total  value  of 
clay  products  marketed  from  this  field  in  1905  was  aboul  $75,000, 
The  demand  for  clay  and  shale  to  he  used  in  the  manufacture  of 
building  material,  tiles,  conduits,  etc.,  will  naturally  increase  as  the 
region  develops  and  as  better  railway  facilities  become  available. 
The  occurrence  of  good  coal  in  quantity  in  this  region  will  do  much  to 
aid  the  development  of  a  considerable  clay  industry. 
At  some  places  in  i  he  held  limestones  with  which  to  mix  the  clay  or 
shale  in  the  manufacture  of  Portland  cement  occur  near  at  hand, 
and  some  <>f  them  are  of  the  proper  composition  for  this  use.  The 
fire  clays  of  the  area  so  far  tested  contain  a  rather  high  percentage  of 
fusible  material,  particularly  iron  oxide,  hut  their  adaptability  for  use 
in  making  semirefractory  products  and  for  lining  copper  converters 
has  been  shown  at  Durango  and  in  copper  smelters  in  Arizona. 
CHARACTER  OF  THE  CLAYS. 
The  clays  of  the  area  may  conveniently  he  classified  as  clay  shales, 
plastic  clays,  and  fire  clays. 
The  clay  shales  include  in  greater  part  the  thick  shale  formations 
of  the  area — the  Mancos  and  the  Lewis — as  well  as  many  thinner  beds 
intercalated  with  the  sandstones  and  coal  beds  of  the  Mesaverde  b  and 
Laramie  formations.     All  of  these  formations  are  of  Upper  Cretaceous 
a  For  a  more  detailed  location  see  reporl  on  i  he  coal  <>i  i his  region  by  M.  K.  Shaler  in  a  forthcoming 
bulletin  of  the  Survey. 
6  For  definition  of  the  Mesaverde  formation  sec  description  of  the  La  Plata  quadrangle,  folio  60,  I '.  S. 
Geol.  Survey,  p.  5,1899. 
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