hillebeand.] CARNOTITE AND ASSOCIATED MINERALS. 21 
An attempt to satisfactorily distribute the constituents among differ- 
ent chemical molecules would be futile, since, for instance, we do not 
know whether to ascribe the barium to a biotite or muscovite molecule, 
but the close approach to the muscovite ratio leaves little room to 
doubt the character of the body. Notwithstanding- the chloritic aspect 
of the mineral under the microscope, the analysis shows that it can not 
be a chlorite, and we have undoubtedly to do with a body closely 
related to the mica roscoelite, wherein, however, the percentage pro- 
portions of A1 2 0. { and V 3 3 are reversed, thus affording a further 
■striking example of the mutual replaceability of these two oxides. 
For comparison, the latest analysis of roscoelite from Placerville, 
(Jal., is included in the above table. Peculiar, though unimportant, 
is the coincidence that the only two known localities for this mineral 
should bear the name Placerville. 
II. GREEN SANDSTONE COLORED BY CHROMIUM. 
Other sandstones that were a much brighter green than the vana- 
liferous one were observed and collected b/y Doctor Ransome, both 
it Placerville and 60 miles distant in Sinbad Valley. The color sug- 
ested a salt of copper as its cause, but analysis showed it to be due 
chromium. Time has not been found to determine the nature of 
lis coloring bod}^. It is very difficultly soluble, and thus presents 
reater hindrance to analysis than did the vanadium compound. It 
vould be interesting to find that it is a micaceous mineral analogous 
o the one just described. Under the microscope it presents a chlo- 
itic appearance (Ransome). If opportunity offers, the problem of its 
lature may }et be attacked. 
In still another greenish sandstone from the west bank of the 
)olores River, near the mouth of La Sal Creek, analysis failed to 
how either vanadium or chromium. 
III. CARNOTITE ORES. 
OPTICAL EXAMINATION. 
Dr. George P. Merrill has kindly submitted the following notes: 
The carno.tite powder appears under the microscope in the form of exceedingly 
inute dust-like particles without crystal outlines and acting so faintly on polarized 
*ht as to at first seem almost amorphous. Much of the matter appears merely as 
fine brownish clay, stained yellow by an amorphous pigment, but occasionally a 
ell-defined fragment of a light-yellow translucent mineral is seen, which doubtless 
presents the vanadium compound in its condition of ideal purity. 
Working over a considerable amount of the powder I have found occasional clus- 
of this yellow mineral in the form of flattened radiating crystals with pyram- 
1 terminations which are without eyident pleochroism, polarize only in dull 
lors, and give extinctions always parallel to the axis of elongation. These are so 
ute (not over 0.25 mm. in length) and so thin that I have never been able to 
d a crystal so oriented as to give an opportunity of determining its exact char- 
r, and I can only say that the general shape is such as to suggest a hexagonal 
eral, though this is by no means certain. 
