254  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
the  coal  would  have  little  or  no  commercial  value,  but  as  the  field  is 
situated  in  one  of  the  most  arid  portions  of  the  country,  in  the  center 
of  a  great  copper-producing  territory,  and  in  a  region  which  is  compar- 
atively rich  in  gold  and  silver,  the  coal  may  have  a  local  value  con- 
siderably beyond  that  which  is  indicated  by  its  chemical  analysis. 
In  a  general  way  the  coal  of  the  Lower  field,  as  seen  by  the  writer, 
and  of  the  Upper  field,  as  reported  by  the  commission  which  examined 
it  in  1885,  occurs  in  two  benches,  in  which  the  coal  differs  con- 
siderably in  quality.  The  first  and  best  grade  usually  is  contained 
in  small  benches  from  10  to  15  inches  in  thickness.  This  is  an 
extremely  hard,  block  coal,  and  has  been  little  affected  by  the  move- 
ments that  have  upturned  the  rocks.  The  other  benches  are  composed 
of  very  much  softer  coal,  presumably  at  first  containing  much  more 
foreign  material.  In  the  movement  which  has  folded  the  rocks  of  the 
basin  this  softer  bench  has  suffered  great  crushing,  and  at  all  points 
where  it  is  accessible  the  coal  is  crushed  into  thin  lamime,  which  show 
much  slickensiding  where  the  particles  have  crushed  together.  Doubt- 
less the  hard  block  coal  would  find  a  ready  market  at  any  of  the  towns 
or  mines  in  the  vicinit}T,  and,  according  to  laboratoiy  tests,  it  can  be 
manufactured  into  coke.  The  softer  coal  is  so  badly  crushed  that  it 
could  be  put  on  the  market  only  as  slack,  and,  as  it  carries  a  heavy 
percentage  of  ash,  presumably  it  could  not  profitably  be  shipped  a 
long  distance. 
The  coal  of  the  upper  field  was  sampled  by  the  commission, a  and, 
as  analyzed  by  Mr.  Edward  Whitfield,  of  the  United  States  Geological 
Survey,  shows  the  following  percentages: 
Analysis  of  coal  from  10- inch  layer  in  bed  opened,  by  tunnel  in  Upper  field. 
Per  cent. 
Moisture 0.  48 
Volatile  combustible  matter 19.  81 
Combined  carbon 61. 01 
Ash,  pink  in  color 18.  70 
Coke Poor. 
Analysis  of  coal  from  10-inch  layer  in  bed  reached  by  crosscut  from  tunnel  in  Upper  field. 
Per  cent. 
Moisture 0.  56 
Volatile  combustible  matter 17.  50 
Combined  carbon 60.  85 
Ash,  pink  in  color 21.  09 
Coke Fair. 
The  commission  also  reports  "the  coal  is  a  hard  bituminous,  and,  as 
tested  in  the  laboratory,  will  make  a  fair  coke,  but  not  so  good  as  that 
from  the  Eaton  district  of  New  Mexico." 
a  Deer  Creek  Coal  Field,  White  Mountain  Indian  Reservation,  Arizona:  Senate  Ex.  Doc.  No.  20,  48th 
Cong.,  2d  sess.,  p.  3. 
