158  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903.  [bull. 225. 
Mountain.  The  occuireneeof  tin  in  placer  deposits  has  been  con- 
firmed on  Anikovik  River,  Buhner  Creek,  a  tributary  of  the  Anikovik, 
and  on  Buck  Creek,  a  tributary  of  Grouse  Creek  which  flows  through 
Mint  River  into  the  Lopp  Lagoon.  Tin  ore  has  also  been  reported 
from  a  great  many  other  localities  which  have  not  been  thoroughly 
examined  by  geologists.  The  tin  deposits,  as  far  as  known,  do  not  fol- 
low any  definite  system,  and  are  confined  to  no  particular  belt  or  zone. 
The  ore,  either  in  lodes  or  in  placer  deposits,  has  been  found  in  asso- 
ciation with .  all  the  sedimentary  formations  above  described.  The 
known  occurrences  of  tin  ore  will  be  described  under  the  headings 
"Lost  River,"  "Cape  Mountain,"  "Buck  Creek,"  "Buhner  Creek," 
and  "Anikovik  River." 
LOST    RIVER. 
Lode  tin  deposits  have  been  found  1  or  5  miles  from  the  coast  on 
Lost  River,  which  enters  Bering  Sea  10  miles  west  of  Port  Clarence. 
Lost  River  has  a  length  of  about  10  miles,  and  drains  the  central  part 
of  the  York  Mountains.  Its  two  tributaries,  Tin  Creek  and  Cassi- 
terite  Creek,  enter  from  the  east  about  3  miles  and  <±  miles,  respec- 
tively, from  its  mouth,  and  tin  ore  has  been  found  on  both  of  these 
creeks.  Cassiterite  Creek,  which  is  really  the  larger  fork  of  Lost 
River,  has  a  length  of  about  3  miles.  Tin  Creek,  about  2  miles  long, 
heads  within  about  a  mile  of  Cassiterite  Creek,  and,  flowing  parallel 
with  it  for  about  the  same  distance,  turns  westward  and  enters  Lost 
River  through  a  canyon  cut  in  the  limestones  of  the  York  Mountains. 
Lost  River  itself  flows  in  a  comparatively  broad  valley  cut  in  these 
limestones.  The  bed  of  the  river  is  not  deeply  gravel  filled,  and  the 
valley  floor  is  practically  cut  out  of  the  limestones  and  not  to  any 
extent  built  on  them.  The  mouth  of  Cassiterite  Creek  is  about  100 
feet  above  the  sea.  In  the  latter  part  of  July,  1903,  Lost  River,  just 
below  this  place,  carried  approximately  1,000  miner's  inches  of  water. 
The  York  Mountains,  in  the  vicinity  of  Lost  River,  are  composed 
almost  wholly  of  ash-gray  Silurian  limestones  showing  little  meta- 
morphism  and  dipping  at  low  angles.  From  the  coast  to  Tin  Creek 
the  limestones  generally  dip  to  the  north,  and  unless  there  be  faulting, 
not  detected  in  the  hasty  examination  that  was  made,  a  thickness  of 
over  4,000  feet  must  be  exposed. 
Dikes  of  igneous  rocks  were  found  cutting  this  limestone  at  several 
places,  and  are  readily  traceable  by  a  growth  of  moss  and  other  vege- 
tation which  forms  over  them,  the  limestone  itself  being  utterly 
devoid  of  vegetation.  Between  Tin  Creek  aad  Lost  River  there  is  a 
boss  or  stock  of  granite  intruded  into  the  limestone,  which  outcrops  in 
a  nearly  circular  area,  probably  half  a  mile  in  diameter.  Around  the 
margins  of  this  area  the  limestone  is  considerably  altered  and  contains 
small  dikes  of  fine-grained  pegmatitic  rock,  presumably  offshoots  from 
the  granite,  cutting  the  limestone  apparently  parallel  with  the  contact 
