Geologic Features
Silicon and oxygen, making up the compound silica, are the two most abundant elements in the earth's crust, and quartz (SiO_2) is a very abundant mineral. The processes of weathering and transportation everywhere operative on the surface of the earth tend to separate quartz from other materials, and to concentrate it into deposits of sand. Katamorphism is primarily responsible for most of the deposits of silica which are commercially used. Anamorphism—cementing and hardening the sands into sandstones and quartzites—has created additional value for certain uses, as in refractories, building stones, and abrasives (see pp. 84, 267).
FOOTNOTES:
[31] Report of the Royal Ontario Nickel Commission. Printed by order of the Legislative Assembly of Ontario, Toronto, 1917.
[32] Campbell, J. Morrow, Tungsten deposits of Burma and their origin, Econ. Geol., vol. 15, 1920, p. 511.
CHAPTER X
COPPER, LEAD, AND ZINC MINERALS
COPPER ORES
Economic Features
The electrical industry is the largest consumer of copper. The manufacture of brass, bronze, and other copper alloys constitutes another chief use for the metal. Considerable quantities of copper sheets, tubes, and other wares are used outside of the electrical industry, as for instance in roofing, plumbing, and ship bottoms. Copper is also used in coinage, particularly in China, where it is the money standard of the working population.
The average grade of all copper ores mined in the United States in recent years has been about 1.7 per cent metallic copper. Ores containing as low as 0.6 per cent have been mined in the Lake Superior country, and bonanza deposits containing 20 to 60 per cent have been found and worked in some places, notably in Alaska and Wyoming. The lower-grade ores, carrying 1 to 3 per cent copper, are usually concentrated before smelting, while the richer ores, carrying 3 to 5 per cent or more, are generally smelted direct. Many of the ores contain values in gold and silver, and also in lead and zinc. An average of about 40c. worth of gold and silver per ton is obtained from all the copper ores of the United States.
In other countries the average grade of copper ores mined is somewhat higher than in the United States,—where large scale operations, particularly the use of steam-shovel methods on extensive bodies of disseminated or "porphyry" copper ores, as well as improvements in concentrating and metallurgical processes, have made possible the use of low-grade ore.
The principal sources of copper are the North American continent, Chile and Peru, Japan, south and central Africa, Australia, and Spain and Portugal. Smaller quantities are produced in Russia, Germany, Norway, Cuba, Serbia, and a number of other countries.
The United States normally produces nearly two-thirds of the world's copper and consumes only about one-third. In addition the great bulk of the South American, Mexican, and Canadian crude copper comes to the United States for refining. Through financial interests abroad and by means of refining facilities, the United States controls a quantity of foreign production which, together with the domestic production, gives it control of about 70 per cent of the world's copper. No other country produces one-sixth as much copper as the United States.
England, because of production in the British Empire (mainly Africa and Australia) and British financial control of production in various foreign countries, is not dependent upon the United States for supplies of raw copper. Japan, Spain, Portugal, and Norway are able to produce from local mines enough copper for their own needs and for export. But France, Italy, Russia, Germany, and the rest of Europe normally are dependent upon foreign sources, chiefly the United States. South America, Mexico, Canada, Africa, and Australia are exporters of copper. The control of these countries over their production in each case is political and not financial, except in the case of Canada, where about half the financial control is also Canadian. It is in these countries and in Spain that the United States and England have financial control of a large copper supply.
Before the war German interests had a considerable control over the American copper industry through close working arrangements with electrolytic refineries. Germany was the largest foreign consumer of copper, and German companies bought large quantities of the raw copper in the United States, Canada, Mexico, and South America, had it refined, and sold the finished material in both the American and foreign markets. During the war this control was broken up.
In view of the importance of copper metal as a raw material, particularly in the electrical industry, the strength of the United States in copper as a key resource ranks even above its control of petroleum.
In the United States in recent years about 40 per cent of the annual production of copper has come from Arizona, chiefly from the Bisbee, Globe, Ray-Miami, Jerome, and Morenci-Metcalf districts; about 18 per cent has come from the Butte district of Montana; about 12 to 15 per cent from Keweenaw Point, Michigan; and about 12 per cent from Bingham, Utah. From 3 to 5 per cent of the country's output comes from each of the states of New Mexico, Nevada, Alaska, and California. All other states together produce only a little over 2 per cent of the total.
The so-called "porphyry" coppers in Utah, Arizona, Nevada, and New Mexico, described below, are the source of about 35 per cent of the present production of the United States. The deep mines of Butte and Michigan are responsible for about 30 per cent of the production, and the ore bodies of Arizona (other than porphyry) and of Alaska produce about 25 per cent.
Reserves of copper ore are such as to give no immediate concern about shortage, nor to indicate any large shift in the distribution of production in the near future. Development is on the whole considerably in advance of present demands. The principal measured reserves are in the so-called porphyry coppers of the United States and Chile. In the United States the life of these reserves now estimated is approximately 25 years. The reserves of the Chile Copper Company are the largest of any known copper deposit in the world, and the Braden copper reserve (also in Chile) is among the largest. For the deep mines of the United States, the developed reserves have a life of perhaps only five years, but for most of these mines the life will be greatly extended by further and deeper development. The porphyry coppers, because of their occurrence near the surface and the ease with which they may be explored by drilling, disclose their reserves far in advance. The deep mines are ordinarily developed for only a few years in advance of production.