from native ores, so that in addition to producing sufficient copper for her own needs the United States has been a heavy exporter for many years.

The most important copper-producing districts in the United States are west of the Rocky Mountains in Montana, Nevada, Utah, Arizona, New Mexico, and California. There are two other important districts, namely, Lake Superior, Mich., and Ducktown, in southeastern Tennessee. More than one-half of the copper consumed in the United States is used in the electrical industries; more than one-fourth in the manufacture of brass, and about one-seventh as sheet copper. The largest exports under normal conditions are to Germany, the Netherlands, and the United Kingdom.

One of the most remarkable advances in mining in this country has been in cheapening the cost of handling copper ore. With the advent of the steam shovel, improved mining methods, and recent advances in concentrating the copper minerals of the ores immense low-grade deposits are now worked at a profit. The resulting gain for industry may be perceived from considering what has been done by five copper companies working such ores in Arizona, Nevada, and Utah. These companies have blocked out and thoroughly tested 590,000,000 tons of ore containing 1.7 per cent copper-10,000,000 tons of metallic copper. Of this copper under the present concentrating and smelting methods, about 75 per cent will be recovered. One of the companies is now recovering 79 per cent. Thus the recoverable copper in the ore bodies of these five companies alone is sufficient to supply all domestic needs at the present rate of consumption for nearly 20 years.

Of the total United States production, the five companies mentioned produced 26 per cent in 1913; other Arizona mines, 26 per cent; the Butte, Mont., district furnished 23 per cent; Lake Superior, 13 per cent; and all others, 12 per cent.

At the present rate of production and recovery these five companies have enough ore actually blocked out to continue operations for nearly 50 years. This does not take into consideration the possible development of new ore bodies as work progresses nor the utilization of known ore bodies containing less than 1 per cent copper, which may be made available by more efficient metallurgical processes. Leaching processes for the recovery of copper are now being tried on a large scale and the results obtained indicate a complete revolution in the metallurgy of copper in the near futurę.

Most of these vast deposits of copper ore were considered a score of years ago too low in grade for profitable mining. At one of these mines previous to 1900 work was being done in a small way and rock that contained 10 per cent or more of copper was considered as

ore; rock of a lower tenor was thrown on the waste dump. To-day at the same mine, through improved methods of mining and milling, all rock with over 0.8 of 1 per cent of copper can be mined at a profit, even with the price of the metal as low as 12 cents per pound. The present market value of the securities of three of the best known "porphyry coppers," the mines being worked by open-cut methods, is over $175,000,000. If the hands of time were to be turned back to the mining and milling conditions of 20 years ago, these properties would have a value little more than what their plants would bring from junk dealers,

These mines are mentioned not only because they show something of the progress made in mining and milling methods, but because they indicate some of the benefits which the Nation derives from such improvements; for three of these mines alone produce about 300,000,000 pounds of copper annually, worth, at 15 cents per pound, $45,000,000. Under the mining and milling conditions of 20 years ago this wealth of copper remained in the earth. Whoever cheapens and perfects processes for recovering metal from low-grade ores that otherwise could not be mined at a profit not only increases the national wealth by the amount of ore recovered but aids the advance toward international industrial supremacy by supplying cheap metal. The extraction of copper by hydrogravity concentration has, up to the present, in spite of much elaboration of process, averaged about 70 per cent. This means that in the United States about 340,000,000 pounds of copper went out with the tailings in 1914. If not recovered, this, with copper at 15 cents per pound, means a loss of $51,000,000 per year. Fortunately, many of the copper mills have ponded their tailings, in the hope that the progress of metallurgical knowledge would some day provide methods to rework them. Within the past year or two some of the companies have begun operations on their accumulated tailings piles, using with considerable success "oil flotation" to recover the metal, and one of the largest companies has put in an elaborate plant for separating the copper in the fine sands and slimes and is now leaching its tailings. However, these companies are only making a beginning, and most of the field yet lies virgin to the investigator.

This problem of trying to save $50,000,000 worth of copper each year from tailings piles is one of large importance to the people of the United States; and yet it is only a small part of the mineral-conservation question of the United States.

LEAD.

The production of lead in the United States in 1880 was 98,000 tons, valued at $9,780,000, but in 1914 it had become 542,000 tons,

valued at $42,280,000, an increase of nearly 600 per cent in tonnage and 400 per cent in valuation. The world produces annually about 1,270,000 short tons, to which the United States, the largest producer, contributes about 32 per cent. Spain ranks second, producing about one-half as much as does the United States.

The normal exports of lead about equal the amount recovered from imported foreign ores and base bullion. As the great bulk of the world's lead is mined and smelted outside of Europe, the European war has not affected the supply as it has that of zinc and some other metals. This country's exports of domestic lead were, however, much larger during the first half of 1915, amounting to 58,000 tons against 20,000 tons for the period July to December, 1914.

The lead mines of the United States were not worked at full capacity in 1914, in spite of the output increasing about 90,000 tons. Large stocks and low metal prices caused many large mines to curtail operations during the last half of the year. The increased mine yield resulted in part from larger recoveries of metal by more efficient milling methods.

These large increases in Missouri, Idaho, and Utah occurred notwithstanding the decline in the average price of lead from 4.4 cents a pound in 1913 to 3.9 cents in 1914, the lowest average price in 16 years.

Lead or lead-zinc ores are mined in 22 States, and the fact that the output increased about 80,000 tons regardless of low prices, shows that the United States can supply its domestic requirements for many years, and can also supply a large export demand if prices are favorable or even equal to the average prices for the last 10 years. Most of the lead and zinc ores of the western States carry silver, which adds to their value.

In brief, the lead resources of the United States are capable of meeting consumption, and the production is only limited by the ability of the market to absorb the output from domestic mines and from ore and base bullion imported from Mexico for smelting and refining.

In addition to the ability to produce all the lead required for domestic use, a large part of the output is "soft" lead or lead free from antimony and other metals, which is easily smelted and is specially adapted for use in lead batteries and for making paints and chemical products.

Approximately 40 per cent of the lead produced in the United States is converted into white lead and pigment for use in paints, and is therefore not recovered as metal. About 15 per cent is used. in the manufacture of pipes for use in chemical industries and in plumbing, and about 7 per cent is converted into sheets largely for

the lining of tanks and receptacles to contain acids and other corrosive substances, uses for which the metal is peculiarly adapted. About 10 per cent of the production is used in the manufacture of shot, and the remaining 28 per cent is used for various purposes.

The most important lead ore deposits are in southeastern and southwestern Missouri, and northern Idaho. There are also large deposits in Utah and Colorado. About 67 per cent of the lead produced in the United States is from Missouri and Idaho. The deposits in both these States are large, and while some are low grade yet improved metallurgical processes and the use of oil flotation in milling will enable these two States to continue to lead the others for many years to come, and to make the United States absolutely independent of foreign countries for the lead it needs.

ZINC.

The world's output of spelter or metallic zinc in 1913 approximated 1,094,000 short tons, of which the United States produced 31.7 per cent. The domestic production, which was higher than that of any other country, was practically all consumed within the United States. The production of zinc in 1880 was 23,240 tons, and in 1913 the total domestic production was 337,000 tons, slightly more than 9,000 tons being produced from foreign ores. The average consumption of spelter for the last 6 years has been about 331,000 tons annually. Since 1880 the zinc output of the United States has increased over 1,500 per cent. Of the total amount produced in 1913, 17,700 tons were exported to Europe. In 1913 Germany and Belgium produced nearly one-half of the world's output of zinc, a larger part from imported ores. The independence of the United States with reference to its zinc supplies, is shown by the fact that from January to June, 1915, more than 64,000 tons of spelter was exported as compared with 824 tons during the corresponding half of 1914. The production of spelter during the last half of 1914 was 178,000 tons as compared with 216,500 tons during the first half of 1915.

The ability to produce spelter is only limited by the capacity of smelting plants, and the high price of zinc has caused all the old coal-fired smelters in Kansas and Missouri to resume operations and has increased the number of retorts in use from 113,914 at the close of 1914 to 130,642 on June 30, 1915. Additional retorts are contemplated and under construction to the number of 34,000, so that within a few months the zinc smelting capacity will be nearly 50 per cent greater than at the end of 1914.

Ores of zinc are so widely distributed that to supply this increased smelting capacity will cause no shortage of ore. Nineteen States

shipped zinc ore in 1914 and about 40 per cent of the spelter produced that year came from ore mines in the Joplin region, in Missouri, Oklahoma, and Kansas. Montana is the second largest producer of zinc ores and large shipments are made from Colorado, Wisconsin, New Jersey, and New Mexico. Tennessee and Arkansas also are producing large quantities of high-grade ores. With zinc concentrates selling at $50 to $60 per ton, many mines in the Joplin region can mine ore that yields 2 to 24 per cent of concentrates. Wisconsin, Alabama, Oklahoma, and other Central States can and will largely increase their output of ore, and the improved methods of concentrating the ore and the higher prices for concentrates will make available large quantities of ore from the Western States.

In the Joplin district, Missouri, about 14 per cent of the ore was left in the mines as pillars. In the West, owing to the cost of treatment and freight charges much low-grade ore is left in the mine, but is not necessarily completely lost unless the mine is wrecked. Except in the New Jersey mines, where conditions are unique, it is probable that less than 50 per cent of the zinc, even in those mines where zinc is the only product, reaches the form of spelter. Zinc mining is frequently done on a royalty basis, an arrangement that means great waste, because the lessee naturally takes out the ore paying the greatest profit and leaves the poorest ore behind. Not only are there enormous losses of zinc in mining, milling, and smelting, but the losses continue in the utilization of zinc, especially in the manufacture of brass. It has been estimated that 15,000 pounds of zinc escape daily up the stacks of the rolling mills in one city in Connecticut.

In concentrating the losses are enormous. In many mills not less than 40 per cent of the metal shown by assaying the ore is lost. From 30 to 35 per cent is perhaps an average loss. In smelting zinc ores the loss is heavier than in smelting any other metal; the average is probably 15 per cent of the assay value.

Lower royalties, better concentration works, and obligatory storage of tailings will help to lessen concentration losses. Further metallurgical improvements are most urgently desirable.

Some 40,000,000 pounds of zinc oxide is used annually for filling in automobile tires, and the remainder of the 60,000 tons now produced annually in the United States is used chiefly in paint. In neither instance is the zinc ever recovered. Dirty foundry scrap, as well as the concentrates from the ashes of crucible furnaces and from molder's sand, are generally worked up in the recovery of copper, the zinc contained, roughly estimated as over 2,000,000 pounds per year, being a total loss.

The annual waste of metals, chiefly zinc, in brass-furnace practice amounts to more than $4,500,000. Two million dollars a year of