GOLD    IN    UINTA    COUNTY.   WYO.,  AND    ON    SNAKE    RIVER.  75 
the  Jurassic  outcrop,  but  cover  the  Bear  River  and  Benton  shale  out- 
crop as  well.  In  neither  of  these  sedimentary  beds  was  there  any  evi- 
dence of  gold  deposits.  In  several  localities,  however  (as  reported), 
fine  gold  particles  or  flakes  have  been  found  in  the  Benton  shale. 
Wherever  found,  the  flakes  are  disseminated  through  the  shale  and 
occur  in  very  small  quantities.  It  is  said  that  two  assays  have  been 
made  of  these  shales  and  that  traces  of  gold  were  found  in  both 
sample:  . 
PLACER    DEPOSITS. 
OCCURRENCE  AND  CHARACTERISTICS. 
Gold  was  observed  at  various  points  on  Snake  River  and  its  tribu- 
taries. It  occurs  either  in  the  gravels  forming  the  terraces  along  the 
streams  or  in  the  deposits  of  bowlders,  gravel,  and  sand  filling  the 
channels  or  forming  the  beds  of  the  streams. 
Interesting  examples  of  terrace  formation  are  seen  on  both  sides  of 
Snake  and  Hoback  rivers  at  points  where  the  valley  expansions  permit 
their  preservation.  At  several  places  along  Snake  River  above  the 
canyon  the  terrace  declivity  shows  a  thickness  of  10  to  15  feet  of  hori- 
zontal stratified  pebbles  and  bowlders  at  elevations  ranging  from  50 
to  100  feet  above  the  river  bed,  and  some  of  the  highest  terraces  are 
as  much  as  200  feet  above  the  river.  The  terraces  slope  gently  toward 
the  center  of  the  valley,  and  their  slopes  are  strewn  with  water-worn 
rock  fragments  similar  to  the  material  found  in  the  river  bed.  The 
material  consists  chiefly  of  quartz,  with -some  granites,  schists,  shales, 
slate,  and  sandstones,  and  here  and  there  some  volcanic  material, 
which  no  doubt  is  derived  from  the  upper  Snake  in  the  vicinity  of  the 
Yellowstone  National  Park.  Snake  River,  between  the  canyon  and  the 
mouth  of  Hoback  River,  occupies  in  many  places  a  wide  shoal  bed  and 
in  autumn  exposes  extensive  bars  of  shingle  and  cobblestone,  among 
which  the  river  winds  in  several  channels.  Many  of  the  terraces  along 
Hoback  River,  below  the  canyon,  extend  back  one-quarter  to  one-half 
mile  from  the  present  river  channel,  whose  bed  is  paved  with  water- 
worn  pebbles  similar  to  the  material  found  in  the  Snake  River  channel, 
the  granites  and  schists  coming  from  the  Gros  Ventre  Mountains  sev- 
eral miles  to  the  northeast.  Near  the  lower  end  of  Hoback  River,  where 
the  stream  cuts  across  two  anticlines  of  low  dip  and  the  eroded  sand- 
stones and  shales  produce  ripples  in  the  stream,  several  flakes  or 
scales  of  gold  were  found  in  the  sands  accumulated  near  the  water's 
edge.  Whether  these  gold  flakes  occur  in  the  gravels  farther  up  Fall 
River  above  the  canyon  and  along  its  tributaries  heading  in  the  Gros 
Ventre  Mountains  was  not  determined.  Numerous  small  streams  that 
emerge  from  the  mountains  can  be  utilized  in  sluicing  operations  or 
for  generating  power  to  run  a  concentrating  plant. 
