hillebrand.] DISTRIBUTION OF VANADIUM AND MOLYBDENUM. 51 
Table II.— Component minerals from certain of the above igneous rocks. 
No. 
7« 
11» 
21» 
23* 
29» 
45» 
46" 
Name and source. 
Amphibole from 7 
Amphibole from 11 
Pyroxene from 21 . . 
Biotite from 23 
Amphibole from 29 
Biotite from 45 
Biotite from 46 
Si()., 
Per cent. 
(?) 
46 
51.5 
36.5 
50 
(?) 
35.5 
V 2 O s = V 2 3 . 
Per cent. 
0.075 
.044 
.043 
.153 
.08 
.057 
Per cent. 
0.062 
.037 
.036 
.127 
M... 
Per cent. 
none 
none 
Table III. — Miscellaneous. 
No. 
Name and locality of occurrence. 
Epidotic schist, Mitchell County, N. C 
Quartz-schist, Madera County, Cal 
Serpentine, Connecticut Valley, Mass 
Sea-green roofing slate, West Pawlet, Vt 
Two red roofing slates (equal parts), Wash 
ington County, N. T 
253 sandstones 
498 building limestones 
Si0 2 . 
v 2 o 5 = 
-v 2 o 3 . 
Mo. 
Per cent. 
Per cent. 
Per cent. 
Per cent. 
48 
0.057 
0.047 
79 
trace 
trace 
38.5 
none 
none 
68 
.017 
.017 
I 56 
| .008 
.007 
78.5 
.003 
.003 
14 
.004 
.004 
Of the igneous rocks specimens were so selected as to represent not 
only many widely separated localities, but also numerous varieties 
from the least siliceous up to those high in silica, in order to ascertain 
whether a preconceived opinion that the vanadium accompanied chiefly 
the less siliceous rocks was well founded or not. The choice was, 
however, confined largely to those rocks analyzed in this laboratory 
within the past three or four years of which a supply of powder 
remained after the original analyses had been completed, and hence 
the list is perhaps not fully representative. Nevertheless it permits of 
drawing certain conclusions, the chief of which is that the vanadium 
predominates in the less siliceous igneous rocks and is absent, or 
nearly so, in those high in silica. The inference, based on the exist- 
ence of the mineral roscoelite, classed as a vanadium mica, at once 
suggests itself, that the ultimate source of the vanadium may be one 
or more of the heavier silicates such as the biotites, pyroxenes, and 
amphiboles, and a few tests on all the available mineral separation 
products lend strong support to this view. For instance, the amphi- 
bole-gabbros 7 and 11 show 0.038 per cent and 0.02 per cent V 2 3 , 
while the amphiboles 7 a and ll a separated from them give 0.062 per 
cent and 0.037 per cent; the pyroxenic gneiss 23 shows 0.083 per cent 
against 0.127 from its contained biotite 23 a ; the diorite 29 with 0.031 
per cent contains an amphibole 29 a with 0.066 per cent; from 0.011 per 
cent in the quartz-mica-diorite 45 and 0.012 per cent in the quartz- 
monzonite 46 the percentages rise to 0.048 and 0.066 in their separated 
