THE  CASHIN  MINE,  MONTROSE  COUNTY,  COLO. 
By  W.  H.  Emmons. 
INTRODUCTION. 
The  Cashin  copper  mine  is  situated  at  Cashin  post-office,  in  the  western  part  of  Montrose 
County,  southwestern  Colorado,  on  La  Sal  Creek,  about  4  miles  west  of  its  junction  with 
Dolores  River.  In  June,  1905,  it  was  the  writer's  privilege  to  make  a  hasty  visit  to  this 
property  incidental  to  a  geological  reconnaissance  under  the  direction  of  Mr.  Whitman 
Cross.  The  nearest  railroad  station,  Place  rville,  on  the  Rio  Grande  Southern,  is  about  70 
miles  to  the  east.  The  wagon  road  between  the  two  points  is  said  to  be  in  very  good  con- 
dition and  of  moderate  grade  for  a  rugged  topography. 
The  region  is  a  portion  of  the  plateau  country  which  under  various  names  constitutes  a 
large  part  of  southwestern  Colorado  and  southeastern  Utah  and  extends  southward  into 
New  Mexico  and  Arizona.  The  country  is  traversed  by  deep  and  relatively  narrow  can- 
yons, the  steep,  inaccessible  walls  of  sedimentary  rock  presenting  a  picture  similar  to  that 
of  the  Grand  Canyon  of  the  Colorado  in  Arizona,  although  the  relief  is  much  less.  The 
climate  is  arid,  but  the  La  Sal  Mountains,  about  10  or  12  miles  to  the  west,  furnish  an 
abundant  supply  of  water  and  power. 
The  deposit  was  discovered  in  1896,  but  active  development  did  not  begin  until  1899. 
Since  then  it  has  been  worked  with  varying  success  most  of  the  time.  According  to  the 
books  of  the  La  Sal  Copper  Mining  Company,  the  present  owners,  it  has  produced  altogether 
363,778  ounces  of  silver  and  732,740  pounds  of  copper. a 
GEOLOGY. 
The  country  is  underlain  by  nearly  horizontal  sedimentary  rocks,  strongly  fissured  and 
faulted. 
The  generalized  geologic  section,  as  observed  in  Paradox  and  Sinbads  valleys  several 
miles  north  of  Cashin,  is  as  follows:  b 
Generalized  section  north  of  Cashin,  Colo. 
Thickness 
in  feet. 
1.  Dakota  formation  (Cretaceous):  Sandstone,  white  or  buff,  often  bearing  abundant  plant 
remains  and  thin  coal  seams 200-400 
2.  McElmo  formation  (Jurassic):  Sandstone  with  shaly  members,  often  massive;  light  pink  or 
white 400 
3.  La  Plata  formation  (Jurassic):  Massive  sandstones,  with  occasional  thin-bedded  or  shaly 
layers ;  pink  or  nearly  white 600-800 
4.  Dolores  formation  (Triassic):  Fine-grained  red  sandstones,  often  thin  bedded,  alternating 
with  sandy  or  calcareous  red  clay  shales.  Contains  one  or  more  beds  of  limestone  conglom- 
erate, usually  bearing  the  remains  of  plants  and  small  pieces  of  bone  ('  Saurian  conglomer- 
ate ") .     Probably  rests  on  Permian  conglomerates 200-400 
a  These  figures  do  not  include  the  shipments  of  native  copper,  of  which  no  record  was  available. 
b  The  writer  was  unable  to  visit  the  country  between  the  mine  and  Dolores  River,  where  that  portion 
of  the  section  which  comes  below  the  present  workings  would  probably  be  exposed.  The  thickness  of 
the  La  Plata  is  exposed  in  the  cliff  above  the  mine,  and  the  persistence  of  the  limestone-conglomerate 
beds  (  'Sadrian  conglomerate")  indicates  that  this  limestone  layer  should  appear  not  far  from  the 
present  lower  workings.  It  could  probably  be  traced  from  its  exposure  south  of  the  Paradox  I) ridge 
up  La  Sal  Creek  and  its  position  below  Cashin  determined  with  some  degree  of  certainty.  It  would  be 
interesting  to  know  what  change,  if  any,  occurs  in  the  ore  body  where  the  fissure  crosses  this  limestone 
member. 
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