14 CONTRIBUTIONS TO MINERALOGY. [bull. 262 
belt, which extends for a distance of about 2,000 feet. When thi 
seam is closely examined it is seen that narrow bands rich in carnotiti 
alternate with green bands carrying mostly roscoelite. There is als< 
usually present a seam of almost pure quartz, generally about ai 
eighth of an inch in thickness, though often thicker. The microscopi 
shows it to be a true quartzite, in which the original rounded detrita 
grains of quartz have been cemented by fresh quartz in optical conti 
iruity with the older granules. A similar quartzite occurs in th< 
green vanadiferous sandstone above the carnotite, where it forms con 
cretionary knots and nodules. It was not noted in the buff sandstone 
however, where the cementing material is calcite. 
Immediately below the carnotite seam there is a parting or " floor' 
in the sandstone, probably originally a very thin layer of shale, whicl 
forms the working floor of the tunnel. The sandstone below thi 
floor is plainly impregnated for a short distance with roscoelite, bu 
the thin shale seam is regarded as the practical bottom of the deposit 
The questions of the origin and actual extent of this deposit an 
closely related and are of much interest. Their discussion will b 
deferred until the other deposits visited have been described. 
Some distance below the Placerville vanadium deposit a zone o 
green sandstone, presumably belonging to the Dolores formation, waa 
observed. This color is a somewhat brighter green than that of tb 
vanadiferous sandstone higher up the slope. As there are some coi 
per prospects near by, from which ore has been taken, this was suj; 
posed to be a copper stain. Qualitative tests by Doctor Hillebrari 
show, however, that the color is due to a compound of chromium. 
Similar green sandstones occur on the western side of Sinbad Vallc 
in what is apparently the La Plata formation, and were original 
supposed to be impregnated with roscoelite. Doctor Hillebranc 
investigations, however, show that they too owe their color to son 
chromium mineral. These occurrences are interesting as showii 
that a green color in sandstones may result from various causes, ai 
that even a bright green tint can not be taken as an infallible indie 
tion of copper. 
LA SAL CREEK DEPOSITS. 
These occur in the extreme western portion of Montrose Count j 
southwest of Paradox, and about 6 miles up La Sal Creek from Cash 
They are reached by trails from Paradox Valley and from Cash 
The deposits are on the south side of La Sal Creek and about 700 frfj 
above the stream. They occur for a distance estimated at more tb 
a quarter of a mile, along the sandstone cliffs which descend from 1 
mesa into the canyon of La Sal Creek, and only a few feet below I 
level of the mesa surface. 
In the absence of continuous stratigraphic work, it is impossi 
to correlate certainly and finally the rocks on La Sal Creek with 
divisions established by Cross and Spencer in the Telluride quadrang J 
