YUKON PLACER FIELDS. 
By L. M. Prindle. 
INTRODUCTION. 
Mining in that part of the Yukon basin which lies in Alaska has, in 1905, been confined to 
he gold placers. In fact, the placer gold is as yet the only resource which has been devel- 
oped, with the exception of a little coal sporadically mined along Yukon River. Gold- 
faring lodes are reported from various districts, but nothing has been found which can 
>e commercially developed under the present high cost of transportation. It is therefore 
oreign to the purpose of this paper to discuss the probabilities of the future growth of a 
[uartz-mining industry in this field. It should be said also that as yet there is little detailed 
nformation on which to base such a discussion. Certain it is that only in small areas does 
he alluvial gold occur in sufficient quantity to permit profitable exploitation. Present 
levelopments indicate that conditions for the occurrence of workable placers exist in the 
IWtymile, Birch Creek, Fairbanks, and Rampart regions. Gold has, however, been 
ound at localities outside of these districts; for instance, in the Salcha basin and in the Bon- 
lerfield and Kantishna districts. Placer gold is also reported to occur in the gravels of 
nnoko River, an easterly tributary of the lower Yukon. 
The Koyukuk district, in the extreme northern part of the Yukon basin, has been a gold 
>roducer for many years. It appears to lie outside of the zone which includes the more 
outherly camps. In mode of occurrence, bed rock, etc., the placers of the Koyukuk « 
losely resemble those of the Yukon-Tanana region. 
In general terms, the belt of metamorphic rocks which enters Alaska at the international 
toundary, between the Yukon and the Tanana region, may be said to be auriferous. This 
>elt stretches westward, or slightly north of west, between the rivers, and touches the Yukon 
n the Ramparts. What is probably a southwesterly extension of the same belt is found in 
he placer-gold districts lying south of the Tanana, but the details of correlation must await 
urther study. 
The outlines presented above define the metamorphic rocks in which the placer gold finds 
js source, but the distribution of the placers is determined by laws only imperfectly under- 
tood. 
Placer mining in the interior of Alaska during 1905 has been unusually successful. A 
actor which contributed largely to this result was the abundant summer rainfall, which 
icreased in quantity from the boundary westward, leaving only the Fortymile region to 
uffer from lack of water. The producing streams are, for the most part, small, the snowfall 
3 generally light, and the streams depend in great measure for their supply of water on t he 
ainfall. Since up to the present time no extensive ditches have been constructed, there is 
i every region a dependence on the supply from streams in the immediate vicinity; and if 
his fails, the work for the summer is largely at a standstill. The rainfall during the working 
Bason, therefore, exerts a controlling influence on the prosperity of a region where condi- 
ions are otherwise most favorable for success. 
a Schrader, F. C, Preliminary report on a reconnaissance along the Chandlar and Koynknk rivers in 
399: Twenty-first Ann. Re.pt. U. S. Geol. Survey, pt. 2, 1900, pp. 482-485. 
109 
