CASHIN  MINE,  COLORADO.  127 
brilliant  blue  of  the  covellite  contrasting  strongly  with  the  dark  chalcocite  and  making  an  ore 
of  unusual  beauty.  The  veinlets  are  generally  approximately  parallel  to  the  direction  of  the 
fissure,  but  sometimes  cut  diagonally  across  it.  Where  the  lode  is  widest,  there  are  four  or 
five  of  these  veinlets.  Frequently  they  play  out  along  a  narrow  seam,  perhaps  to  reappear 
beyond.  Carload  shipments  of  the  rich  ore  have  given  returns  as  high  as  512  ounces  of  silver 
ito  the  ton.  Large  masses  of  the  native  copper  occur  embedded  in  the  kaolin,  especially  in 
Jthe  lowest  level.  Most  of  them  are  irregular  bodies  about  as  thick  as  they  are  long,  and  one 
was  found  which  weighed  over  500  pounds.  A  sheet  of  leaf  copper  was  observed  on  the 
dump.  It  was  about  a  foot  square  and  one-eighth  of  an  inch  thick,  and  was  slickensided  on 
Iboth  sides.  Native  copper  also  occurs  in  veinlets  with  calcite  and  barite,  and  one  shipment 
(averaged  89  per  cent  copper  and  77  ounces  of  silver  to  the  ton. 
TREATMENT   OF   THE   ORE. 
On  account  of  the  excessive  hauling  charges,  only  the  high-grade  ore  can  be  profitably 
shipped.  Of  this  ore  the  mine  has  produced  2,067  tons,  which  averaged  12.5  per  cent  copper 
and  134  ounces  of  silver  to  the  ton. 
The  Russel  leaching  process,  by  which  the  roasted  and  erushed  ore  was  treated  with  a  weak 
solution  of  hyposulphite  of  soda,  proved  successful  so  far  as  the  silver  was  concerned,  recov- 
ering 89  per  cent  of  the  values,  but  it  was  too  expensive  for  the  recovery  of  the  copper.  By 
this  method  3,100  tons  were  treated  at  the  mine,  yielding  an  average  of  3.5  per  cent  copper 
and  28  ounces  of  silver  to  the  ton.  A  small  smelter  was  also  installed.  Iron  pyrite  was 
shipped  from  Ophir,  Colo.,  and  coke  from  Dakota  coal  was  obtained  from  ovens  about  4  miles 
west  of  Naturita,  or  28  miles  east  of  the  mine.  The  product  was  a  copper  matte  running  high 
in  silver. 
PROBABLE  ORIGIN   OF  THE  ORE. 
S.  F.  Emmons,«  in  reviewing  the  occurrence  of  copper  in  the  "  Red  Beds ' '  of  the  Colorado 
Plateau,  mentions  a  large  number  of  deposits  which  are  found  in  sedimentary  rocks  far  from 
outcrops  of  contemporaneous  or  later  igneous  rocks.  In  regard  to  the  origin  of  some  of  these 
occurences,  his  observations  "  favor  the  idea  that  the  ore  has  been  leached  down  from  above 
and  is  of  secondary  origin,  rather  than  that  it  is  an  original  deposit  from  uprising  solutions." 
F.  L.  Ransome,b  in  discussing  the  uranium  and  vanadium  minerals,  which  occur  in  the  La 
Plata  sandstone  of  the  Colorado  Plateau  near  Placerville,  Colo.,  and  elsewhere,  suggests  that 
the  deposits  of  these  minerals  "are  local  concentrations  from  the  bulk  of  the  sandstone." 
The  ore  deposits  at  Cashin  probably  belong  generically  to  the  same  class,  though  they  are 
distinctly  fissure  deposits.  It  is  always  possible  that  an  igneous  body  may  underlie  any 
sedimentary  rock,  and  the  laccolith  which  formed  the  La  Sal  Mountains  may  have  sent  out 
thin  intrusive  sheets  between  the  sediments  to  points  much  nearer  Cashin  than  those  at 
which  these  rocks  now  outcrop;  but  such  intrusive  sheets  were  not  observed  at  any  of  the 
places  where  they  should  be  revealed  at  points  nearer  the  La  Sal  Mountains  than  the  Cashin 
mine  and  at  horizons  lower  in  the  sedimentary  series. 
The  general  occurrence  of  small  bodies  of  low-grade  copper  minerals  in  the  "  Bed  Beds"  of 
the  Colorado  Plateau  suggests  these  formations  as  a  possible  source  of  the  Cashin  ores.  The 
sedimentary  rocks,  consisting  mainly  of  massive  sandstones  alternating  with  thin-bedded 
sandstones  and  shales,  dip  toward  Cashin  from  the  La  Sal  Mountains.  Their  higher  outcrop 
is  several  thousand  feet  above  their  outcrop  at  Cashin,  and  the  dip  of  the  beds  is  approxi- 
mately the  slope  of  the  surface.  The  water  circulation  is  down  the  dip  from  the  higher 
country,  and  where  the  rocks  are  cut  through  by  erosion  it  manifests  itself  as  springs  in 
the  deeper  valleys.  Often  these  springs  are  highly  charged  with  salt  or  alkali,  and  some 
of  them  contain  considerable  quantities  of  hydrogen  sulphide.  Such  springs  were  noted  in 
Fisher  Creek  Canyon  north  of  the  La  Sal  Mountains.  It  is  not  known  whether  or  not  these 
waters  carry  a  trace  of  copper,  but  some  of  them  are  at  least  capable  of  dissolving  copper, 
a  Bull.  U.  S.  Geol.  Survey  No.  260,  1905,  p.  221.  &  Am.  Jour.  Sci.,  August,  1900,  p.  120. 
Bull.  285—06 9 
