ZINC
Zinc is a whitish metal. It is used in galvanizing iron to prevent its rusting. It is used also in the manufacture of white paint, which consumes about one ton out of every six tons mined. This, of course, is permanently lost, but the price and its value as a resource is much lower than lead. This takes more than half of the entire product. The remainder of the output is about equally divided between brass and sheet zinc. All these uses are extremely necessary and it is believed that the production of zinc will rapidly increase for many years.
The United States is the largest producer, Germany ranks second. Large amounts are mined in Australia, and very large deposits, entirely undeveloped, are said to exist in Africa. In 1880, the United States produced 23,000 tons of zinc; in 1907, 280,000 tons. This indicates the rapid rate at which we are increasing our use of zinc.
If the same rate should continue, in 1920 we should be using 475,000 tons, or almost a billion pounds, and if zinc oxide should take the place of white lead in painting to the extent that now seems probable, the quantity would be still further increased.
Missouri is by far the heaviest producer of zinc, having a little more than half of the output. New Jersey ranks next, then Colorado, Wisconsin and Kansas. Some of the other western states each produce small amounts. Most of the pure zinc ore is mined at a depth of from one hundred and fifty to two hundred and fifty feet and occurs in sheets, but a large part of the ore is a by-product obtained from the reduction of other ores. In New Jersey the zinc alone is found in a single region, where it was estimated a few years ago that there were eight million tons, of which two and a half million tons have been mined since 1904. The zinc in Missouri, Wisconsin and Kansas is found alone or underlying lead deposits, while that of the western states is almost always found in limestone, and is mixed with silver, copper, lead, and, more rarely, gold. In these states there has been little attempt to discover zinc; in fact, ores containing zinc have been rather shunned because of the difficulty in extracting them.
It is thought that our resources of zinc, especially in the West, have just begun to be developed, and that the supply, even at the present rate of increase and at present prices, will last many years. However, with increasing use for the product, we can not be sure of supplies for more than a generation; and in view of the importance of zinc it becomes necessary to inquire into its wastes.
In no mineral is the waste more startling than in zinc. In Missouri it is necessary to leave supporting pillars as in coal mining. This can not be remedied, as the use of timbers is too expensive, but it causes a heavy loss. In the West, owing to the expensive treatment and shipment, much of the low-grade ore is left in the ground. In refining the loss is enormous, often as much as forty per cent. In order to produce zinc at a low cost there must be a heavy loss of metal. Better plants and equipment for refining, and the saving of all refuse for later use will be necessary if we are to conserve the zinc supply for future generations.