288 ECONOMIC GEOLOGY 



preceding year. The production was delayed at Seven Troughs 

 by a cloudburst in July and the mill at National was burned in 

 September. On the other hand there was an increased production 

 in the Manhattan, Fairview, and Round Mountain districts. 



In Colorado also there were several fluctuations in the gold 

 mining camps. The San Juan district, which includes the counties 

 of Dolores, La Plata, Ouray, San Juan, and San Miguel, showed 

 a decrease of about $1,000,000. This came largely from the 

 Camp Bird mine on Sneffels creek. The Cripple Creek district 

 increased its output by nearly $400,000, due in part to the 

 successful drainage by the Roosevelt tunnel. Montana, Utah 

 and Washington each showed a decreased production. 



The gold mining industry in South Dakota gave the largest 

 output in the history of the state, the increase being about 

 $400,000 over the output of 1911, due largely to activities in the 

 Homestake mines. The large hydroelectric plant of the company 

 owning these mines was completed and put into operation in 

 1912. 



California retains the rank of the first producer which position 

 she wrested from Colorado in 1911. Nevada, Alaska and South 

 Dakota are also large producers. 



Gold dredging was especially active in California and Alaska 

 where increased dredging capacity was added. The 120 dredges 

 in operation in 10 states including Alaska produced more than 

 $10,000,000 of gold. 



According to the Geological Survey, in 1911, the gold and 

 silver mills produced 53.8 per cent, of the output, the placers 

 24 per cent., and the large smelting plants 22 per cent. Of the 

 product from the gold and silver mills 26 . 1 per cent, was produced 

 by cyanidation, 23.9 per cent, by amalgamation, and 3.8 per 

 cent, by chlorination. Dredging alone gave 10.9 per cent. 



During the past few years there has been a general decline in 

 the prospecting, and no notable discoveries of new ore bodies 

 or deposits that seem likely to give immediate material increase 

 to the annual output of gold have been effected. The ore bodies 

 in some of the large camps, as at Goldfield, already show a diminu- 

 tion in the value per ton of ore mined. 



Imports and Exports. According to estimates made for the 

 Survey by the Bureau of Foreign and Domestic Commerce, the 

 imports of gold for 1912 were valued at $61,400,000. The 

 exports for the same year were valued at $48,600,000, The 



