Ch. 1: Gold and Silver in 1918

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	GOLD AND SILVER.	775

	PERCENTAGE OF OUTPUT OF GOLD AND SILVER PRODUCED BY DIFFERENT PROCESSES. Percentage of output of gold and silver produced by different processes, 1913-1918.



	The placers produced about 23.2 per cent of the total output of gold—a decrease of 2.6 per cent. The dredges produced nearly 18 p er cent less gold in 1918 than in 1917, and the combined placer yield from hydraulic, drift, and other surface methods was about $5,540,000 less than in 1917. The decrease from placers was largely due to a smaller output from Alaska, California, and Oregon. The percentage of output of silver credited to the placers is insignificant. In the mills the amalgamation process showed a loss of 0.2 per cent of the total recovery of gold in 1918. This was due to the decrease in mining and milling in Colorado, California, and South Dakota, which produce ores more amenable to treatment by amalgamation. The gold recovered by cyanidation showed an increase of 2.5 per cent, following an increase of 1.4 per cent in 1917. Colorado, Nevada, Arizona, Oregon, and South Dakota ores yielded the larger part of the gold recovered by cyanidation. The chlorination process was only used in a few mills in California and the output of gold therefrom was less than 0.2 per cent of the total recovery of gold. None of the Colorado plants used chlorination in 1917 and 1918, and the total recovery of gold by that process in California mills amounted to $119,173.

	GOLD AND SILVER PRODUCED AT MILLS, BY STATES. A large quantity of concentrates from sulphide ores is now smelted, and the increased application of the flotation process has resulted in decreased yield of gold and silver from cyanidation, as.nearly all such concentrates are shipped to smelters. The smelters, which had for two years been producing each year a slightly greater proportion of gold and silver, are to be credited in 1918 with about 23.9 per cent of the total output of gold and 85.3 per cent of the silver. The bulk of the production of gold remains mainly from the gold mills. As shown by the table above the proportion of gold recovered

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