(>2 FORTYMILE, BIRCH CREEK, AND FAIRBANKS PLACERS. ! bull. 251 
the cut. Work can be commenced here about June 15 and continued 
to about September 20. 
Mastodon Creel-. — The headwaters of Mastodon Creek are gathered 
from an amphitheatral area on the northern slopes of Mastodon 
Dome, 4,400 feet high, situated about 7 miles southwest from the 
point where the creek enters Mammoth. The creek flows through a 
picturesque valley limited by even-topped spurs, which slope gradu- 
ally in a direction parallel to the creek at an altitude of about one- 
fourth mile above it. The valley is unsymmetrical in section, the 
stream in its lower portion approaching the steep ridge on the east, 
and beinc: bounded on the west bv a bench which rises with a steep 
grade to the base of the spur. Farther upstream the valley becomes 
more open and the stream flat attains a width of several hundred feet. 
Quartzite-schist and mica-schist are the most common varieties of 
bed rock and contain the usual proportion of quartz veins. The 
strike of the schistosity is usually across the stream and the dip to 
the south. Near the mouth of the Mastodon some thin-bedded, 
impure, closely folded limestone was observed. On some of the 
claims occurs a greenish feldspathic schist which weathers more easily 
than the usual bed rock, and may represent an intrusive rock which 
has undergone metamorphism along with the other rocks. Small 
granitic dikes also occur. 
The gravels are similar in character to those on the Deadwood. They 
include subangular fragments of the bed rock, with fine material of 
the. same nature and some sand and clay. A large part of it is but 
little worn, and the arrangement is generally more or less irregular. 
The average depth to bed rock is 10 to 12 feet, with a maximum of 
about 20 feet. There is sometimes a layer of muck on top of the 
gravels, which attains a thickness of about 4 feet. Seven feet is the 
maximum of stripping that is required. The gold is found sometimes 
scattered through the gravel and sometimes close to bed rock or to a 
distance of a few feet within it. The pay streak has a variable width, 
with a maximum of perhaps 200 feet. The gold is generally rather 
fine, the coarsest piece found thus far weighing only 3 or 4 ounces. 
Some of the ground averages probably from $2 to $3 a cubic yard, 
and some of it is considerably richer. Estimates of the annual pro- 
duction have been made varying from $75,000 to over $100,000. The 
gold brings $17 an ounce in trade. 
Work, the results of which are said to be satisfactory, is being done 
on the rim to the west of Mastodon. The gold is somewhat coarser 
than the creek gold. Portions of the creek have been worked thor- 
oughly and systematically by the open-cut method. At one locality 
11 parallel cuts, each 18 feet wide, have been run. (See PI. XIV, B.) 
It is said to require about twelve days' work of one man to shovel a box 
length 18 by 12 feet, with an average depth to bed rock of about 8 
