ORE  DEPOSITS  OF  THE  OURAY  DISTRICT,  COLORADO. 
By  J.  D.  Irving.0 
LOCATION  AND   GENERAL  FEATURES  OF  THE  DISTRICT. 
The  town  of  Ouray,  Colo.,  long  an  important  mining  center  and 
now  chiefly  known  as  the  place  from  which  one  may  most  readily 
reach  the  Camp  Bird  mine,  is  situated  in  the  San  Juan  Mountains, 
in  the  southwestern  part  of  Colorado. 
It  occupies  a  broad,  flat  bottom  land,  nearly  circular  in  form  and 
about  one-half  mile  in  circumference,  which  lies  at  the  center  of  the 
forks  formed  by  the  junction  of  Canyon  Creek  and  the  Uncompahgre 
River. 
The  two  streams  enter  the  valley  from  deep  precipitous  gulches, 
while  the  Uncompahgre  River  leaves  it  by  a  narrow  canyon  which  is 
cut  through  the  dark  red  sedimentary  rocks  of  the  Carboniferous 
system.  A  mile  farther  north  the  canyon  widens  and  the  Uncom- 
pahgre emerges  into  cultivated  bottoms  that  stretch  away  to  the 
northwest.  The  valley  in  which  the  town  is  situated  has  the  appear- 
ance of  being  almost  completely  encircled  by  abrupt  cliffs,  but  these 
are  broken  on  the  west  by  the  gorge  of  Oak  Creek  and  on  the  east 
by  the  green  hills  that  rise  above  the  town  and  form  the  bottom  of  the 
steep-sided  Portland  amphitheater. 
The  metalliferous  deposits,  which  it  is  the  chief  purpose  of  this 
paper  to  discuss,  are  all  near  the  town  and  mainly  occupy  the  pre- 
cipitous country  on  the  two  sides  of  the  Uncompahgre  River.  No  one 
of  the  important  mines  is  at  a  greater  distance  from  Ouray  than  3J 
miles. 
The  ore  deposits,  although  they  include  only  a  few  highly  pro- 
ductive mines,  form  a  series  of  very  unusual  scientific  interest,  one 
which  it  is  thought  may  throw  some  light  on  a  number  of  the  vexed 
questions  of  ore  deposition. 
Their  salient  features  are  intimately  related  to  the  geology  of  the 
region,  and  the  following  summarized  discussion  of  the  geology  (by 
Dr.  Ernest  Howe)  is  essential  to  a  clear  comprehension  of  their 
character: 
a  With  a  note  on  the  geology,  by  Ernest  Howe. 
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