126 GUIDEBOOK OF THE WESTERN UNITED STATES. 
At Elliston the red shale of the Kootenai (Lower Cretaceous), fol- 
lowed by the dark shale of the Colorado, is visible on both sides of 
the valley. A short distance below the town there is a 
large area of dark-red lava (rhyolite) which extends 
as far as milepost 35. From this point westward for 
some distance the valley is much broader than it is 
near Elliston, and at some stage of the Tertiary period contained a 
lake. The sediment deposited in this lake can be seen on the right 
(north) along the track as far as Avon (see sheet 18, p. 134), except . 
where a sharp ridge of rhyolite east of the town 
extends from the right and just crosses the railway 
track. Beyond Avon Little Blackfoot River enters 
a rugged canyon, at first in red rhyolite and then in 
thin-bedded red sandstone of the Belt series (Algonkian). These 
rocks continue a short distance beyond milepost 41 and are separated 
from the Cretaceous rocks to the west by a small mass of igneous 
rock (andesite) that has been intruded along the fault. 
The lowest formation of the Cretaceous and the first to be seen in 
traveling westward is the Kootenai, which is visible on the left. 
This formation, characterized by bands of bright-red shale, is 
few hundred feet thick and is overlain by Upper Cretaceous rocks 
which extend continuously from this place to Garrison. This over- 
lying formation is undoubtedly the same as the Colorado shale far- 
ther east, but its composition is different. In the eastern localities it 
is mostly a dark shale with only here and there a bed of thin sand- 
stone, but along the Little Blackfoot it is composed of a succession 
of beds of sandstone and shale with sandstone predominating. 
tons, or triple the quantity of anthracite 
mined in Pennsylvania in the last cen- 
tury. When all the known deposits in 
Elliston. 
Elevation 5,061 feet. 
St. Paul 1,160 miles 
Avon. 
Elevation 4,702 feet. 
St. Paul 1,169 miles. 
give off a fetid odor when struck with a 
hamm 
these four States have been examined in 
detail i 
uggests the roe of a fish.) 
The rock is composed of rounded grains 
ranging in size from the tiniest specks to 
rock usually has a 
netlike k 
phosphate is appreciably heavier than 
? ies 
On account of the high cost of trans- 
portation the present market of the west- 
ern phosphates is confined to the Pacific 
' - In 1914 the western phos- 
phate field furnished 5,030 tons, valued 
at $15,488, or an average price of $3.08 a 
ton. This is about one-fifth of 1 per cent 
of the total phosphate production of the 
United States, which in 1914 amounted to 
soluble phosphates for use in th 
ture of fertilizers by treatment with 
sulphuric acid. As this acid can be made 
to the miners of phosphate but also to the 
smelter men and the farmers. 
