RANsome.] CARNOTITE AND ASSOCIATED MINERALS. 15 
which lies just east of this area. It seems probable, however, that the 
La Plata sandstone attains a much greater thickness in this portion of 
western Colorado than it does between Telluride and Placerville. The 
limestone bed, so characteristic a feature of the formation near Placer- 
ville and farther east, is not uniformly present in this western region, 
and the La Plata sandstone (Variegated beds, in part, of the Harden 
survey) is not always readily differentiated from the underlying 
Dolores formation (Red Beds). For a vertical distance of about 400 
feet above the bed of La Sal Creek the rock is a heavy-bedded, rather 
fine-grained, light-colored sandstone, which is considered by Doctor 
Spencer to be the La Plata. Above this come thinner-bedded sand- 
stones, with some conglomerates and shales, which are included in the 
McElmo formation. It is in this upper series that the uraniferous 
deposits occur. All the beds are here approximately horizontal. 
As revealed b}^ numerous small openings near the crest of the bluff, 
the carnotite, which is the material here sought, is found chiefly in a 
massive bed of nearly white sandstone. Some of the ore, however, 
lies between the sandstone and a lower bed of light-gray shale. 
Although the prospecting openings all lie at about the same level 
uong the cliffs, the deposit is not nearly so regular as the vanadif erous 
band near Placerville. 
The carnotite of La Sal Creek occurs as irregular, bunchy u pockets" 
n the sandstone, or along the contact of the sandstone with the under- 
ying shale. These have all the appearance of being impregnation 
leposits, the solutions carrying the uranium compounds having depos- 
ted the ore wherever they found ready passage through the rock — usu- 
tlly along bedding planes. No roscoelite was seen with the earnotite. 
The most remarkable and interesting fact in regard to the La Sal 
>eek deposits is their very superficial character. The ore bodies are 
isually flat-lying streaks, a few inches thick, which grade above and 
[>elow into the common light-buff sandstone, and which die out and 
jlisappear when followed into the hillside. In tunnels that run but a 
jew feet underground the yellow impregnation of carnotite can be seen 
Tadually to die out and to be succeeded by light-colored sandstone, 
howing no trace of the mineral. It is doubtful whether any appre- 
iable quantity of carnotite occurs as much as 20 feet from the surface, 
n any of the locations, although this distance is given from memory 
nd not from measurements on the ground. As before stated, the 
I npregnation has usually taken place along bedding planes; it has also 
roceeded along surfaces of minor and superficial movement in the 
ocks. In one case it was observed that a portion of the overlying 
mdstone had moved upon the underlying shales, the disturbance being 
pparently a superficial one, of a kind commonly enough observed 
here massive beds rest on yielding shales on a steep hillside. In 
ther words, the movement appeared to be directly related 'to the 
resent topography. 7'he carnotite was here deposited subsequent to 
