26 TIN DEPOSITS OF THE YORK REGION, ALASKA. [no. 229. 
BROOKS MOUNTAIN. 
This mountain lies about 11 miles north of the mouth of Lost River. 
The locality can easily be reached by a road up Lost River from the 
beach, or by a road following up Don River from Port Clarence. 
Wagons have been driven over both these routes. By the latter route 
the mountain is probably 20 miles from deep water of Port Clarence. 
The bed rock exposed on the mountain consists of highly altered lime- 
stones, and black slates which resemble the slates near York/' 
The sedimentary rocks are cut by a number of granite and rhyolite 
dikes, which are believed to strike approximately east and west. All . 
of the streams which head in Brooks Mountain, namely Lost River, 
Don River, York River, and Mint River, carry granite bowlders that 
have been derived from the mountain. 
In 1901 the writer observed in this vicinity some of the minerals 
that have been found associated with tin in the ledges seen within the 
past season, and in the winter of 1901 a prospector, who had spent 
considerable time in this same region, sent a collection of these min- 
erals to the Geological Survey Office. This collection contains a great 
deal of tourmaline and garnet, both of which are associated with tin 
ore on Tin and Cassiterite creeks, about4 miles south of Brooks Moun- 
tain. This locality seems promising for the occurrence of tin-bearing 
veins, though so far as is known to the writer no tin ore has yet been 
identified. 
DON RIVER. 
On the west side of Don River there is a ridge of high hills com- 
posed, in part, of slates like those found near York. h 
These slates are cut by intrusive dikes of quartz-porphyry and 
granite resembling the intrusives of Brooks Mountain and Lost River. 
Some of the minerals often associated with tin ore have been found 
here, and the region is worthy of some investigation. This region 
lies about 10 miles east of Lost River and 9 miles north of Port 
Clarence. 
EAR MOUNTAIN. 
Ear Mountain is 50 miles north of Teller and 10 miles southwest 
from Shishmaref Inlet, a large, shallow body of water, not navigable 
for ocean vessels. Should the reported discoveries of tin be verified, 
and the ore occur in commercial quantities, a railroad not over 50 miles 
in length could be built to Port Clarence. 
This mountain is an isolated upland mass that has an altitude of 
« Collier, A. J., A reconnaissance of the northwestern portion of Seward Peninsula, Alaska: Prof. 
Paper U. S. Geol. Survey No. 2, 1902, p. 30, PI. III. 
b Collier, A. J., Idem, pp. 46-47. 
