SILVER Any attempt to evaluate the world's resources in silver is com plicated by the fact that so much of it is produced in connection with other metals, notably lead, copper and gold; almost every gold mine produces some silver and every silver mine some gold. The three largest silver-producing States of the United States are Utah, Montana and Idaho; in the first two silver is produced chiefly in connection with copper, and in the latter in connection with lead ores. About one-third of the silver in the United States is derived from what are primarily copper ores, one-third from lead ores and the remainder from all other kinds, including those which are simply silver ores. The silver content of many of these ores is so low that they could not possibly be worked for silver alone, so that an evaluation of silver resources becomes an esti mation of the resources of copper, lead, zinc or other deposits which are important producers of silver.
Silver occurs in rocks of all geologic ages from the oldest to the most recent. It also occurs in nearly all countries of the world, so that nearly all of them are able to produce at least some part of their requirements. China, until recently one of the principal silver-consuming countries of the world, produces very little silver, and it is not understood where its early silver supply was obtained. The Comstock lode in Nevada was discovered in 1859; by 1877 its annual production had reached $22,000,000 in silver, and for a long period this deposit furnished half the silver output of the United States, its total output of silver to 190o being estimated at $220,000,000. Its output since 1886, when most of the deep mines in the lode were abandoned, has been relatively small. With the decline of the Comstock district the Leadville district in Colo rado took its place as the greatest silver district of the world. Sil ver production there reached its peak (over $ii,000,000) in 1881, followed by a gradual decline until 19o7, since when it has re mained at about $2,000,000 annually. The silver production of Canada was about 5,000,000 oz. per year until 1905, when the Cobalt district was discovered; in 1910-13 the output was over 32,000,000 oz. per year. Eight years later it was about 13,000,000 oz. ; now it is over 20,000,000 annually. The average yearly pro
duction of the world for the period 1901-22 was 188,000,000 oz., ranging from 163,000,000 to 226,000,000; in 1937 it was 273,322, 943 ounces. Mexico produces about one-third of the total ; the United States about one-fourth, and Canada and South America each contribute about one-tenth.
The principal use of silver is in coinage, and the industrial arts. Photographic and chemical uses (which are the only ones in which silver may be said to be consumed) require an annual amount estimated at from io,000,000 to 20,000,000 ounces. It is evident therefore that there are two reserves of silver, unmined ore and the accumulated stock of metal. It seems certain that the world can produce for a long period enough silver for the uses by which it is actually consumed. How long it can produce enough to supply needs for coinage and industrial arts depends not only on the dis covery of new silver-producing districts, and the production of metals with which it is associated, but also to the extent to which silver coins may be replaced with token coins made of other more abundant metals. The policy followed by the United States Gov ernment, since 1934, of stimulating domestic production by an artificially high price, while buying in world production in an attempt to raise the price of silver to $1.29 per ounce, has resulted in an accumulation of an idle stock of over 75,000 tons. It is pos sible also that other metals may be substituted for silver in its uses in the industrial arts, since developments in the art of chro mium plating and in the production of non-corrosive alloy steels make it possible to produce at a reasonable price metal articles that will not tarnish. It is possibly safe to imply that no new silver-producing district like Cobalt will be discovered, and the principal additional supplies of silver for future use are likely to be copper, lead, zinc, and other metal deposits where the large tonnage involved may yield considerable quantities even though the amount per ton is small. However, the copper deposits of Africa, the largest additions to the reserves of that metal recently developed, contain no important silver reserves. (T. T. R.)