HII.1F.RKAM..1 CARNOTITE AND ASSOCIATED MINERALS. 31 
On the improbable assumption that the iron is to be wholly included, 
and regarding only the water given off above 300°, the following- 
ratios result: 
H t .;? R' g6 K'\ll R' '«5 ^727 Qw78J 
which become, if the iron is excluded, 
H±67 -K 86 R 114 R 111 ^ 51 727 ^2462* 
These figures, while strongly suggesting definite ratios between 
certain of the constituents, do not under the circumstances warrant 
the deduction of a formula, nor do they lead to the same conclusion as 
in the case of the green cementing material of the sandstone at Pla- 
cerville. The phengite-muscovite ratio of that is not apparent here; 
yet it is not at all unlikely that a mineral like the one from Placerville 
is present, but contaminated with some other. In fact it would be sur- 
prising to find anything but a mixture in sandstones so thoroughly 
altered. The very existence of such vanadiferous transition products 
is itself highly interesting, and these tedious analyses were not there- 
fore made in vain. The mud-like amorphous character of this material 
precludes any hope of aid from the microscope in solving the question 
of its homogeneity. 
SUMMARY. 
The body called carnotite is probably a mixture of minerals, the 
exact nature of which analysis fails to reveal. Instead of being the 
pure uranyl-potassium vanadate, it is to a large extent made up of 
calcium and barium compounds. Intimately mixed with and entirely 
obscured bj^ it is an amorphous substance — a silicate or mixture of 
silicates — containing vanadium in the trivalent state probably replac- 
ing aluminum. 
The deposits of carnotite, though distributed over a wide area of 
country, are for the most part, if not altogether, very superficial in 
character and of recent origin. 
The green coloring and cementing material of certain sandstones 
near Placerville, Colo., is a cryptocrystalline alumino-vanadio-potas- 
sium silicate resembling roscoelite, but with the percentage propor- 
tions of A1 3 3 and V 2 3 reversed. It constitutes over 25 per cent of 
portions of the sandstone, and contains nearly 13 per cent of V 2 3 , the 
atter amounting in the maximum case observed to 3.5 per cent of the 
sandstone. 
As yet (1900) these highly vanadiferous sandstones have been found 
)nly at Placerville, where it is intended to work them for vanadium. 
Carnotite is associated with them in only trifling amount. 
Other sandstones noticed owe their bright green color to chromium. 
In yet another case where the color was dull green this was not due 
o either chromium or vanadium. 
