CLAY    DEPOSITS    IN    NEW    MEXICO    AND    COLORADO.  299 
San  Juan  district^-The  clay  industry  of  the  San  Juan  district  is 
limited  to  Animas  and  San  Juan  valleys,  New  Mexico.  In  Animas 
Valley,  at  Farmington,  a  small  brick  plant  has  been  in  operation  since 
1900,  and  at  Flora  Vista  and  Aztec  bricks  have  been  manufactured 
since  1903.  The  production  of  this  valley  finds  an  outlet  to  Colorado 
markets  over  the  branch  line  of  the  Denver  and  Rio  Grande  Railroad, 
which  has  recently  been  constructed  down  the  valley  from  Durango. 
In  1903  a  plant  at  Farmington  successfully  began  the  manufacture  of 
what  is  known  as  "granite  blocks,"  a  building  material  manufactured 
largely  from  clay. 
In  San  Juan  Valley  a  production  of  building  brick  was  reported 
from  Fruitland  by  Biggs  &  Stephens  in  1901.  At  Jewett  and  Ship- 
rock  building  brick  to  supply  a  local  demand  were  produced  in  1903. 
At  Shiprock  the  Government  Indian  School  and  Agency  buildings 
were  constructed  during  1904  and  1905  of  brick  made  on  the  ground 
from  Mancos  shale. 
In  both  Animas  and  San  Juan  valleys,  excepting  in  cases  already 
noted,  residual  clays  are  used  in  the  manufacture  of  brick.  The 
product  is  common  red  building  brick,  and  the  market  is  local. 
Gallup  district. — The  Gallup  district  centers  about  Gallup,  N.  Mex. 
The  clay  industry  at  Gallup  and  Clarkville,  a  coal-mining  camp 
about  4  miles  west  of  Gallup,  consists  almost  wholly  of  the  produc- 
tion of  semirefractory  fire  clay,  which  is  shipped  to  the  copper  smelt- 
ers of  southern  Arizona,  there  to  be  used  for  the  purpose  of  lining 
copper  converters.  Two  companies  at  Gallup  and  one  at  Clarkville 
are  now  producing  this  semirefractory  fire  clay.  At  the  Clark  mine 
at  Clarkville  and  at  one  place  at  Gallup  the  clay  is  worked  in  con- 
nection with  coal  mining.  In  the  Rocky  Cliff  mine  at  Gallup  the 
clay  bed  is  from  10  to  20  feet  thick  and  lies  between  two  coal  beds. 
After  the  lower  coal  bed  is  taken  out  the  timbers  are  removed  and 
the  fire  clay  is  allowed  to  fall;  then  the  upper  coal  bed  is  mined. 
Two  or  three  cars  of  this  clay  are  shipped  every  day  from  this  mine 
to  southern  Arizona. 
Just  south  of  the  town  limits  of  Gallup  fire  clay  has  been  mined 
for  five  years  by  the  Rocky  Cliff  Coal  Mining  Company.  The  bed 
varies  in  thickness  from  7  to  1 1  feet.  No  timbering  is  necessary,  as 
the  Jbed  is  immediately  overlain  by  a  bed  of  massive  sandstone. 
Until  recently  the  production  of  this  mine  was  rather  large,  two  or 
three  cars  being  shipped  daily  for  use  in  Arizona  smelters. 
At  Clarkville  there  are  several  beds  of  this  semirefractory  clay, 
varying  in  thickness  from  1  to  20  feet.  The  beds  lie  comparatively 
flat  and  are  of  wide  areal  extent.  About  12,000  tons  of  clay  are 
produced  annually  at  the  Clark  mine,  and  this  production  has  been 
continuous  since  1898.  The  clay  is  all  shipped  to  the  United  Verde 
Copper  Company,  at  Jerome,  Ariz.,  where  it  is  used  for  lining  copper 
