NICKEL    DEPOSITS    OF    NICKEL    MOUNTAIN,  OREGON. 
THE    ORE    AND    THE    GANGUE. 
123 
Practically  all  the  known  occurrences  of  nickel  silicate  in  this 
region  are  within  an  area  of  1£  square  miles,  lying  on  the  slopes  to  the 
south,  southwest,  and  southeast  of  the  mountain.  The  thin  soil 
peculiar  to  this  area  is  composed  almost  entirely  of  iron  oxides,  which 
give  it  a  distinctly  reddish-brown  color.  The  ores  occur  chiefly  as 
flat-lying  deposits  on  the  surface  of  the  peridotite  and  subordinately 
as  veinlets  in  the  peridotite  or  its  decomposition  product,  serpentine. 
Only  one  nickel  mineral  is  known  to  occur  in  these  deposits,  namely, 
genthite,  which  is  a  soft  hydrous  nickel-magnesium  silicate.  The 
proportions  of  the  nickel  and  magnesium  vary  considerably  in  the 
best  specimens  obtainable,  as  shown  by  the  subjoined  analyses: 
Analyses  of  nickel  silicates  from  Riddles,  Oreg. 
* 
1. 
2. 
3. 
4. 
Loss  at  110°  C 
8.87 
6.99 
1.18 
44.73 
10.56 
27.  57 
} 
6.  63 
1.  38 
48.  21 
1ft  90 
23.88 
7.00 
1.  33 
40.55 
21.70 
29.66 
12.29 
AI2O3+  Fe-.()  -j 
.06 
Si02       
48.82 
MgO 
18.49 
NiO                                          
19.04 
99.90 
100.  00 
100.  24 
98.70 
1.  Clarke,  F.  W.,  Am.  Jour.  Sci.,  3d  ser.,  vol.  35,  1888.  p.  484. 
2-3.  Hood,  Dr.,  Mineral  Resources  U.  S.,  1882,  U.  S.  Geol.  Survey.  1883,  p.  404. 
4.  Von  Foullon,  II.  B.,  Jahrbuch  K.  k.  geol.  Reichsanstalt,  vol.  42,  1892,  p.  272. 
There  is  probably  every  gradation  from  material  with  compositions 
like  those  of  the  foregoing  analyses  to  pure  silicate  of  magnesium. 
Von  Foullon"  states  that  he  was  able  by  washing  to  separate  from  the 
green  ores  of  Nickel  Mountain  a  light-colored  material  which  on 
analysis  proved  to  be  magnesium  silicate,  containing  no  nickel.  The 
color  of  the  genthite  varies  with  the  nickel  content  from  a  pale  green 
to  a  deep  green — the  more  nickel  present  the  more  intense  the  color. 
For  the  sake  of  comparison  some  analyses  of  the  best  nickel  silicates 
of  New  Caledonia  are  given  herewith : 
Analyses  of  New  Caledonia  nickel  silicates. & 
1. 
2. 
3. 
4. 
5. 
17.97 
.55 
38.35 
10.  61 
6. 
7. 
IT2o 
15.  40 
.89 
42.61 
18.27 
15.55 
.50 
35.45 
2.47  i 
10.34 
1.68 
44.40 
3.45 
.43 
1.07 
38.  61 
15.83 
1.57 
37.  78 
10.06 
17.60 
.11 
37.49 
14.97 
12.73 
Al203+Fe203.... 
3.00 
Si02 
47.90 
MgO 
12.51 
FeO 
CaO ,. 
NiO 
21.  91 
45.  15 
33.  91 
32.52 
29.72 
24.  00 
99.08 
99.  12 
99.  98 
99.75 
100.  00 
99.89 
100. 14 
<i  Jahrbuch  K.  k.  geol.  Reichsanstalt,  vol.  42,  1892,  p.  232. 
b  Annales  des  Mines,  10th  ser.,  vol.  4,  1903,  p.  368. 
