GOLD    TN    UINTA    COUNTY,   WYO.,  AND    ON     SNAKE    RIVEK.  81 
rearing  gravels  for  which  Snake  River  is  noted.  The  dredge  was 
>perated  by  the  Sweetzer-Burroughs  Dredging  Company,  of  Minidoka, 
vfiose  plant  and  methods  were  described  in  detail  in  the  Engineering 
tnd  Mining  Journal,  February  15,  1902  (reprinted  in  the  report  of 
he  Idaho  inspector  of  mines,  for  1904).  This  plant  was  a  suction 
Iredge  that  ran  several  years  and  handled  3,000  cubic  yards  per  day, 
laving  probably  about  half  of  the  gold  content  of  the  gravel  raised 
Tom  the  low  bars  in  and  along  the  borders  of  the  stream  between 
ligh  and  low  water  marks.  This  company's  operations  commenced 
n  the  spring  of  1894,  when  it  practically  had  the  choice  of  the  stream. 
[Tie  results  obtained,  the  best  layers  of  gravel  being  skimmed  to 
ibout  6  feet,  averaged  all  through  less  than  10  cents  per  cubic  yard, 
yter  several  years  of  continuous  operation,  which  resulted  in  one 
£10,000  dividend,  the  enterprise  was  abandoned,  as  the  possible  margin 
)f  profit  was  too  small  to  warrant  its  continuance. 
Robert  N.  Bell,  in  writing  of  the  Snake  River  gravels  in  the  vicinity 
)f  Minidoka,  Idaho,  makes  the  following  statement:  a 
I  am  skeptical  about  the  invisible  gold  contents  of  these  gra"\  °1  deposits,  except 
he  coated  gold,  which  is  readily  recognized.  The  Snake  River  fine  gold  is  finer  than 
my  natural  placer  gold  that  I  know  of.  It  is  high  grade,  but  requires  fully  1,000 
,o  1.500  colors  to  weigh  1  cent  in  value.  Yet  under  a  powerful  microscope  each 
X)lor  is  an  individual  nugget  showing  abrasion  marks.  These  particles  are  even 
coated,  touched,  or  spotted  with  a  crystalline  white  film,  with  some  foreign  substance 
hat  looks  like  silica  under  the  glass,  and  this  is  what  makes  it  necessary  to  polish  it 
n  the  grinding  pan  before  it  will  amalgamate  freely.  The  size  of  the  particles  ranges 
within  comparatively  narrow  limits,  but  there  is  no  gradual  shading  from  the  smaller 
colors  into  imperceptible  dust,  and  if  the  gravel  contains  any  invisible  gold  that  can 
lot  be  recognized  in  an  ordinary  pan  with  the  naked  eye,  it  must  be  locked  up  in  the 
^articles  of  heavy  concentrates. 
The  Government  dam  at  Minidoka  has  raised  the  water  over  an 
adjacent  high  terrace  that  represents  an  old  river  bed  and  contains 
some  of  the  best  values  in  fine  gold  along  Snake  River.  This  terrace 
s  known  as  Diamond  Bar,  and  the  shallow  water  now  covering  it 
affords  a  pond  with  sufficient  water  to  float  a  chain-bucket  or  suction 
Iredge,  either  one  of  which  is  adapted  for  treating  this  ground.  A 
plan  to  dredge  the  terrace  has  lately  received  considerable  attention 
Tom  promoters,  and  already  one  company  has  organized  and  pur- 
chased several  claims  near  the  lower  end  of  the  backwater,  with  a 
new  of  installing  a  dredge  and  taking  advantage  of  the  favorable 
situation  created  by  the  Government  irrigation  enterprise. 
In  May  and  June,  1906,  before  the  water  was  ponded  above  the 
lam,  some  prospecting  on  these  gravels  was  done  by  the  United  States 
Greological  Survey.  The  land  examined  by  L.  G.  Gillette  and  W.  L. 
Walker  consisted  of  certain  claims  along  Snake  River  in  Idaho  which 
would  be  submerged  when  the  lake  formed  by  the  dam  at  Minidoka 
a  In  a  letter  to  the  writer,  January  12,  1907. 
