GOLD-BEARING   RIVER    SANDS    OF    N.   E.  WASHINGTON.  69 
diate  flood  plain  of  the  stream,  and  the  gold  is  of  local  origin.  Below 
Alkire  the  sands  of  the  Sanpoil  Valley  were  tested  at  a  number  of 
places,  almost  invariably  with  negative  results,  though  a  few  colors 
of  gold  were  obtained  near  Keller.  No  deposits  of  gold-bearing  gravel 
that  will  justify  the  expectation  of  successful  development  occur  along 
Sanpoil  River  at  any  point  except  those  noted  on  West  Fork. 
ORIGIN   OF  THE   GOLD. 
The  ultimate  source  of  the  Columbia  River  gold  is  to  be  found  in  the 
areas  of  crystalline  and  metamorphic  rocks  to  the  north  and  east, 
which  are  known  to  contain  gold-bearing  quartz  veins,  as  well  as  other 
ore  bodies  of  various  kinds  containing  gold.  Millions  of  tons  of  such 
rocks  were  washed  away  in  the  formation  of  the  river  valley,  and  the 
deposits  with  which  the  valley  was  filled  during  the  glacial  period  rep- 
resent many  millions  more,  the  gold  content  of  which  has  been  con- 
centrated in  river  bars.  Much  of  this  gold  has  doubtless  been  carried 
many  miles,  but  that  some  of  it  is  of  comparatively  local  origin  is 
indicated  by  the  coarse  flake  gold  found  on  some  of  the  bars.  Some- 
what coarser  and  rougher  colors  of  gold  were  obtained  from  the  bed  of 
a  small  creek  several  miles  from  the  Columbia.  It  is  probable  that 
there  are  many  such  tributary  streams  in  which  colors  of  gold  can  be 
found  which  have  added  small  amounts  to  the  gold  deposits  of  the 
river. 
METHODS    OF  MINING. 
The  mining  and  collecting  of  finely  divided  gold  like  that  along  the 
Columbia  is  hie vit ably  more  difficult  and  requires  greater  care  and 
skill  than  ordinary  placer  mining.  The  appliances  which  have  been 
used  are  rather  simple  forms  of  rocker  or  sluice  box  equipped  with 
blanket,  carpet,  or  burlap  riffles.  Neither  quicksilver  nor  copper 
plates  are  used  in  the  boxes.  In  sluicing,  the  material  is  invariably 
passed  over  some  form  of  grizzly  which  screens  out  the  finer  part  and 
drops  it  to  an  undercurrent  or  spreads  it  over  tables  where  the  gold 
is  collected.  The  Chinese  probably  ground  sluiced  before  shoveling 
the  pay  dirt  into  the  boxes.  In  two  places  where  white  men  were 
mining  last  summer  the  whole  deposit  above  the  pay  streak  was 
hydraulicked  and  washed  into  the  sluice  with  water  under  a  small 
head  from  a  canvas  hose.  One  of  the  principal  difficulties  in  mining 
this  gold  is  encountered  at  the  clean  up.  The  gold  is  associated  with 
such  great  quantities  of  black  sand  that  it  is  almost  impossible  to  sep- 
arate it.  The  usual  method  of  collecting  the  gold  with  quicksilver  is 
laborious  and  expensive,  often  fails  to  extract  much  of  the  gold,  and 
utterly  fails  to  collect  platinum  if  it  is  present.  Experiments  made  at 
the  concentrating  pavilion  at  Portland  have  demonstrated  that  this 
separation  can  be  accomplished  economically  by  means  of  a  Wilfley 
concentrator,  but  even  by  this  means  the  expense  of  mining  would 
probably  not  be  greatly  reduced. 
