Ch. 1: Gold and Silver in 1922

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	618	MINERAL RESOURCES, 1922—PART I.

	Some of the States produced comparatively small quantities of copper ore containing considerable gold and silver, but the copper ores of the major copper-producing States contained very little gold and silver. In 1922 the lead ores of Utah showed an average recovery in gold and silver of $16.85 a ton, and the lead ores of Idaho, the leading State, only $4.13 a ton. In the output of ore considered as producing gold and silver, the proportion of dry and siliceous ore decreased greatly, being 24.8 per cent, compared with about 39 per cent in 1921, the proportion of lead ores decreased from 9.5 to 6 per cent, whereas that of copper ores increased from 50 to 66 per cent. The proportion of other classes of ore, which together comprise only 2.75 per cent of the total, also increased considerably. The average value per ton in gold and silver of siliceous ores, copper ores, lead ores, and zinc ores increased in 1922, whereas that of copper-lead and lead-zinc decreased. The following table shows that copper ores comprised 66.3 per cent of the ore containing gold and silver mined and treated during the period 1906-1922, dry and siliceous ores 24.3 per cent, and all the other classes of ore 9.4 per cent. The peak of production of dry and siliceous ores was reached in 1916, though the proportion of such ores to the total was largest in 1906. The extraction value varies considerably in different years, depending to a large degree on the quantity of low-grade ores milled in Alaska and South Dakota. The quantity of copper ores exceeded that of dry and siliceous ores by only 1,250,000 tons in 1906, whereas in 1918 the excess was about 43,700,000 tons, owing to the great activity at the large properties having low-grade disseminated deposits of copper ore. The output of copper ores during the last four years was very much less than in the years 1916-1918. The decided decrease in the average extraction value of gold and silver in copper ores was caused by the low gold and silver content in the greatly increased quantity of copper ores derived from mines in Arizona, New Mexico, Nevada, and Utah. The average extraction value of gold and silver was only 56 cents a ton in 1922, against $1.55 a ton in 1906. In 1914, owing to the low price of silver, the average extraction value was only 49 cents. The quantity of lead ore containing gold or silver mined and treated during the period 1906-1922 has ranged from 1,815,243 tons in 1919 to 2,563,904 tons in 1913. As silver predominates over gold in most of the lead ore the average extraction value shows a wider range than the quantity of ore. Zinc ores comprised less than 1 per cent of the total ore given in the following table, and the average extraction value in precious metals shows a considerable range. The copper-lead and copper-lead-zinc ores have been negligible in quantity but show a higher average extraction value than any other class of ore. The lead-zinc ores containing gold and silver decreased greatly in 1921 and 1922, though they comprise about 3 per cent of the total ores given in the table and have averaged in gold and silver nearly $3 a ton.

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