Ch. 1: Gold and Silver in 1916

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	684	MINERAL RESOURCES, 1916—PART I.

	IMPORTS AND EXPORTS. Value of gold and silver imported and exported, 1916. (Figures furnished by the Bureau of Foreign and Domestic Commerce.)



	DOMESTIC SUPPLY. The remarkable gain in domestic supply of gold indicated by the great excess of $530,200,000 in imports over exports for 1916, or $73,000,000 more than the world's total output of new gold for the year, was due to the fact that this country has been a creditor nation since the last great movements of its gold abroad. The continuation of large exports of silver to the Far East, and especially to the entente nations in Europe, was due largely to demand for exchange and for the coinage of silver money for troops in the field. The domestic supply of new gold comes chiefly from dry or siliceous gold ores, treated in gold mills by amalgamation or cyani-dation, or both, and from placer gravels largely by dredging. As shown on page 707 these ores and placer gravels supplied 88 per cent of the yield of gold in 1916. Examples of gold-milling ores are those of the Homestake mines of South Dakota, the Goldfield mines in Nevada, the Grass Valley and Mother Lode mines of California, the Alaska mines of the Juneau district, and the Cripple Creek and upper San Miguel County mines in Colorado. The great gold-dredging fields of California, especially of the MarysviTle district, are examples of the placer gravels as worked on a large scale. A considerable output of gold is also now recovered from the refining of copper bullion from copper ores, especially of the West Mountain or Bingham district, Utah, the Robinson or Ely district, Nev., and the Summit Valley or Butte district, Mont. In 1916 the copper ores of the United States produced more than 9 per cent of the total gold, against 7.2 per cent in 1915. The natural tendency is for the proportionate output from gold ores to decrease, with declining yield

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