164 
CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
Remits  of  concentration  of  black  sands — Continued. 
d.  Lots  in  which  the  reduction  of  values  in  the  tailings  is  complete,  but  the  weight  of  the 
concentrates  is  much  too  large. 
Record 
num- 
ber. 
P99 
P89a 
P102f 
P46 
P86 
P67b 
Locality  from  which  sample 
was  obtained. 
CALIFORNIA. 
Del  Norte  County:  Crescenl 
City. 
Humboldt  County:    Cold 
Bluff. 
Coos  County:  Randolph  dis- 
trict, beach. 
Curry  County: 
Cold  Beach 
Chetco 
Josephine  County 
Material. 
Concenl  rates  Nos.  1,  2,  and  3.. 
Tailings 
Concentrates  No.  1 
'tailings 
Concenl  rates  Nos.  1,  2,  and  3. 
Tailings 
Concentrates  Nos.  1  and .2. 
Tailings 
Concenl  rales  Nos.  1  and  2. 
Tailings 
Concentrates  Nos.  1  and  2. 
Tailings 
Amount. 
Pounds. 
837 
459 
41.5 
175.  5 
385 
171 
49 
58.25 
429.2 
36.8 
157.5 
565.5 
Actual  value  of 
gold  and  plati- 
num in  product. 
Dollars. 
0.120 
.0 
.647 
.  000 
.142 
.00 
.041 
.001 
.050 
.  0004 
.153 
.00 
Per  cent. 
78.49 
.00 
99.17 
99.  81 
2.  56 
73. 09 
.66 
100.  80 
e.  Lots  in  which  the  values  arc  so  minute  that  concentration  has  failed  to  reduce  the 
in  the  tailings  and  the  assays  fail  to  check  up. 
alues 
I'N'le 
P105 
P81b 
P26 
P101 
P87a 
CALIFORNIA. 
II  ii  m  boldl  County:    Gold 
Bluff. 
IDAHO. 
Ada  County:  Boise. 
B  i  ngh  a  in  County:   Quaker 
River. 
OREGON. 
Baker  County:  Sumpter 
Coos  County:  Whiskey  Run, 
7  miles  north  of  Bandon. 
Curry  County:  Port  Orford.. 
]( !oncen1  rales  Nos.  I  and  2. 
[Tailings 
Concentrates  Nos.  1  and  2. 
Tailings 
Concent  rates  Nos.  1  and  2. 
Tailings 
Concentrates  Nos.  1  and  2 
Tailings 
Through  |  mm.: 
( Joncentrates  Nos.  1  and  2. 
Tailings 
Concentrates  Nos.  1  and  2 
Tailings 
96.  5 
986 
7 
289 
3 
12 
5.5 
96.5 
1.  93 
23. 07 
82 
476 
0.0(11 
.291 
.017 
.001 
.002 
.004 
.018 
.0008 
.0013 
.  026 
.047 
9.50 
45.  25 
15.04 
69.76 
35.  L6 
75.25 
17.08 
83.32 
39.07 
60.  77 
31.46 
56.30 
It  is  evident  from  the  above  results  that  a  great  majority  of  the  black  sands  arc  suf- 
ficiently valuable  to  justify  separation  into  their  various  mineral  constituents  by  concen- 
trating tables  of  the  Wilfley,  Pinder,  Woodbury,  and  Christensen  types;  and  it  is  evident 
also  that  the  effective  operation  of  these  tables  is  comparatively  independent  of  the  fine- 
ness of  the  gold,  since  in  many  sands  gold  as  fine  as  200-mesh  is  readily  saved  on  the  tables — 
frequently  from  95  to  98  per  cent  of  the  total  assay  value. 
Further  examination  of  black-sand  localities  and  of  concentrating  methods  during  the 
remainder  of  the  fiscal  year  1906  has  been  recommended  by  the  Secretary  of  the  Interior. 
