BLACK  SANDS  FROM  PLACER  MINES. 
L59 
Gold  and  'platinum  contained  in  black-sand  concentrates  from  various  placer-mining  districU 
by  States  and  counties — Continued. 
Number  of  sample. 
State  and  county. 
District. 
Ounces  per  ton 
of  concentrate. 
Gold. 
Plati- 
num. 
D  2030 
Oregon— cont'd. 
Josephine 
do 
Allen  Gulch  mine.  Waldo 
37.  30 
None. 
2.  GO 
2.  40 
Trace. 
(i.  36 
Trace. 
0.58 
D  2013 
Coyote  C  reek 
D  2025... 
South  Santiam  River 
3  52 
D  2001 . . , 
Camp  Carson  district,  C!  rande  Rondo  River 
12 
D  9504... 
SOUTH  DAKOTA. 
D  15516 
UTAH. 
Garfield 
Colorado  River 
.  15 
D  15511 
FIELD    WORK. 
Economy  of  time  required  that  the  examination  of  the  conditions  of  occurrence  of  the 
j    heavy  minerals  in  placer  gravels  should  be  undertaken  long  before  the  laboratory  specimens 
!    had  been  completed.     Therefore  a  corps  directed  at  first  by  Prof.  J.  F.  Kemp,  of  Columbia 
j    University,  New  York,  proceeded  to  the  well-known  localities  on  the  Pacific  slope  where 
•previous  examinations  had  shown  the  gravels  to  contain  considerable  percentages  of  min- 
erals heavier  than  quartz. 
Investigation  of  sands  at  the  mouth  of  Columbia  River. — On  account  of  the  accessibility  and 
the  slight  cost  of  transporting  the  sands  to  the  concentrating  headquarters  at  Portland,  an 
investigation  was  promptly  undertaken  of  the  seashore  sands  at  the  mouth  of  Columbia 
River.  Mr.  A.  H.  Gale,  field  assistant,  visited  Astoria  and  examined  the  coast  sands  from 
that  point  on  the  river  beach  to  the  mouth  of  the  river  at  Fort  Stevens  and  southward  on 
the  Pacific  beach  to  Tillamook  Head,  a  total  distance  of  about  15  miles.  The  beach  sands 
of  this  region  are  limited  by  a  clay  ridge  extending  from  Tongue  Point  about  6  miles  inland 
from  the  mouth  of  Columbia  River  southwest  to  the  ocean  beach  at  Tillamook  Head.  The 
triangle  formed  by  this  ridge  and  the  ocean  and  river  contains  a  great  variety  of  sands  which 
can  be  roughly  grouped  as  follows: 
Beginning  at  Tillamook  Head  the  beach  is  made  of  heavy  bowlders  diminishing  in  size  to 
the  north  until  within  less  than  a  mile  they  change  into  heavy  dark-green  sands  containing 
a  small  proportion  of  magnetite  and  other  heavy  minerals  and  a  little  quartz.  Farther  up 
the  beach  the  sands  are  gradually  lighter  in  color,  with  a  much  larger  proportion  of  quartz, 
until  the  mouth  of  the  river  is  reached.  The  jetty  extending  from  Fort  Stevens  northwest 
to  the  deep  channel  has  caused  light-gray  sands  to  fill  in,  building  out  the  shore  from  the 
original  beach  about  one-half  mile  and  doubtless  burying  deposits  of  much  heavier  sand 
such  as  those  immediately  adjacent  on  the  river  beach.  These  sands  on  the  south  side  of 
the  mouth  of  the  river  are  exceptionally  black  and  contain  a  large  proportion  of  magnetic 
iron  ore  and  other  heavy  minerals.  To  the  east  from  the  ocean  beach  the  usual  sand  dunes 
are  encountered,  consisting  largely  of  quartz  sand  with  very  little  magnetite  or  other  heavy 
minerals.  Still  farther  east,  up  to  the  clay  ridge  which  limits  the  beach  sands,  the  sands 
show  an  increasing  percentage  of  clay,  but  only  exceptionally  carry  any  interesting  propor- 
tion of  heavy  minerals.  This  region,  bounded  on  the  east  by  the  clay  ridge  extending  from 
Tongue  Point  to  Tillamook  Head,  is  known  as  Clatsop  Plains. 
Mr.  Gale  selected  five  carloads  of  the  sand  from  this  region,  one  of  which  represented  the 
green  sand  on  the  beach  in  the  neighborhood  of  Tillamook  Head;   another  the  heavy  black 
Bull.  285—06 11 
