METHODS OF PRODUCTION.

Very nearly all the zinc ore mined in the United States must be concentrated before shipment to the smeltery. There is some production, especially of carbonate ore, that needs only to be roughly sorted by hand to bring it up to a grade that will be accepted by smelters, but by far the greater part of the domestic zinc ore must go through a more or less complicated dressing operation.

There are no particular features that distinguish the mining of zinc ores from the mining of other metals, such as copper and lead. As a rule the ores are not unusually hard and are easily extracted by standard methods of underground mining. Extensive ope

tions on a large scale as exemplified in the working of the copper properties are not in vogue. Deposits of zinc ore comparable to the "porphyry" deposits of copper in the Southwest are unknown. The nearest approach to this condition are the zinc areas near Joplin, but that district is characterized by the great number of small operators. A similar condition exists to a considerable degree in other sections of the United States. Zinc mining as well as smelting has been peculiarly free from large combinations of capital and, with the exception of perhaps a half dozen exceptionally large producers, most of the zinc mines are operated independently.

The amount and character of treatment necessary for the preparation of a salable product from zinc ores as they come from the mine will vary widely according to the deposit and the locality. For certain ores, notably those containing zinc as the only recoverable value or those in the Mississippi Valley region where the zinc and lead are easily separated, comparatively simple ore dressing is sufficient. Little machinery and equipment is required, and the amount of capital necessary for the successful conduct of a small mine and mill is so small as to permit the development of individual ownership or operation by little companies. On the other hand, the successful utilization of many of the complex ore deposits which are characteristic of the Rocky Mountain region calls for the highest metallurgical skill, complicated equipment, and a considerable outlay for plant, in addition to the cost of developing the ore body to the point of production.1

A great many mines are equipped with mills, but these mills rarely do much if any custom work. Joint ownership of mines and smelting works is rare, as ownership of mines has never been the important feature of the zinc industry."

HISTORY.

The oxide ores of New Jersey, Pennsylvania, and Wisconsin were the early sources of ore supply for smelting operations until after the Civil War. As early as 1774 a shipment of red zincite was made from Franklin Furnace to England under the impression that it was copper ore. This same district also furnished the first spelter produced in the United States. Only one small lot was turned out and was used for making the brass for the Government standard set

1 This subject will be discussed more fully in another section of this report.

2 Even the German control of the European zinc situation before the war was obtained almost wholly through ownership and regulation of the production of reduction works and through long-term contracts for the ore output of independent mines (notably in Australia).

of weights and measures in 1838. It is also reported that during the War of 1812 some brass was made from these same ores, probably by the cementation process.

No zinc was produced in Missouri until 1867, when small works were erected at Potosi, but lead had been mined since 1848 in Jasper County, near Joplin, and the presence of zinc must have been early recognized. The first zinc ore from the Joplin district was marketed in 1872, and in the following year the production became important. The ore was shipped at first to Illinois for smelting. Joplin rapidly increased in importance and became the leading producing district in the United States.

As the lead mines of Wisconsin, Virginia, Colorado, and other states were developed the zinc resources of this country were better recognized. For many years zinc was considered a detrimental ingredient of ores and, in the early history of many camps, an excess of zinc was the cause for closing down properties that might otherwise have been profitably worked. Nearly all the large zinc-producing districts were originally opened up for the production of other metals.

An important factor in the zinc-mining situation has been the development of separation processes for the recovery of zinc from other sulphides and gangue. One of the earliest successful devices was the standard Joplin jig, which proved highly advantageous for the treatment of the coarser sizes of the comparatively simple combination of galena and sphalerite, present in that region. Next came the Wilfley concentrating table that allowed a similar separation on all material down to the slime sizes. The latter machine even permitted a partial elimination of pyrites, a mineral of only slightly greater specific gravity than blende. Slime tables followed, but were not so successful in the preparation of clean products.

As the treatment of complex ore developed a great demand arose for a process that would make a valuable zinc product out of the "zinc-iron" middling. Various methods have proved more or less satisfactory, notably roast-magnetic and electrostatic separation. Preferential flotation is now an important probability and has been successfully applied in many cases.

DOMESTIC RESOURCES AND LOCALITIES OF PRODUCTION.

Zinc deposits are found in almost every State in the Union, and in 1917, production was reported from 23 States. In spite of this wide. distribution, however, over 80 per cent of the total output of the United States is furnished by six districts. These are (1) MissouriKansas-Oklahoma (Joplin or "Komspelter"), (2) New Jersey (Franklin Furnace), (3) Montana (Butte), (4) Wisconsin, (5) Colorado (Leadville, Red Cliff, and Breckenridge), (6) Idaho.

The first named is the largest zinc producing region in the world, and has contributed approximately one-seventh of the annual output of the world in recent years. This region, which goes by several names, lies mostly in southwestern Missouri, more or less adjacent to Joplin, but also overlaps contiguous territory in Kansas, Okla

186.6 per cent in 1917.

homa, and Arkansas. The ore is typically zinc-lead, and contains no precious metals.

The activity in this district reflects the state of the zinc market. The production comes from a large number of small individual operators, many of them marginal producers or "leasers" who can operate their mines only when the ore can be sold fairly readily at a price more or less above the occasional minimum prices that result from market fluctuations. If the low prices continue for more than one or two weeks, these weaker producers have to quit and go to work elsewhere, perhaps on farms or in the city. A large proportion of the ore smelters are situated in that vicinity, attracted not only by the nearness to the ore supply but also because of the availability of cheap fuel, both coal and gas. Its importance is therefore even greater than the figures of its actual production, which were equal in 1917 to more than one-third of the total for the country.

New Jersey, the second largest producer, is remarkable for the unusual character of the ore in its one important district, Franklin Furnace. The deposits there are the only ones of the kind in the world. The peculiar purity of the ore and its abundance and grade have been the foundation of the success of the largest single zincproducing corporation in the world, the New Jersey Zinc Co. New Jersey furnished 16.7 per cent of the domestic output of zinc in ore in 1917, and its proportion of the total output of grade A or high-grade ore suitable for the manufacture of the purest grades of spelter is much greater. It is the most important factor in the pigment trade, as the best grades of American process zinc oxide are made from these ores.

Colorado was the third largest producer for many years but has been surpassed by Montana. In 1915 both of these States were furnishing approximately 13 per cent of the domestic output; but in in the active development of the next two years, Colorado failed to increase its tonnage rapidly enough to keep pace with other parts of the country, and dropped to fifth position, supplying only 8.3 per cent of the domestic total in spite of the fact that its actual tonnage output increased slightly. Montana produced 13.1 per cent of the total United States mine production of zinc in 1917. Wisconsin, which in 1915 was in fifth place among the zinc-producing districts, furnishing 7 per cent of the domestic total, increased its proportion to 8.4 per cent, or slightly more than that of Colorado. Idaho is the sixth State in order of production, supplying 5.6 per cent of the total output of the country in 1917.

The ores of all these districts are different from either of the first two types. Wisconsin ores are the most nearly similar to those of Missouri, but invariably contain much greater amounts of iron sulphide, together with arsenic and antimony. The difficulty of separating these from the blende delayed the economic development of of these areas for a long time. long time. The ores of the Rocky Mountain States are invariably complex in the number of metals present, but here their resemblance to one another ceases. The Montana ore can be easily concentrated to a product containing 50 per cent and more of zinc. In addition to zinc some copper, a little lead, and importan silver values are present in the concentrate.

In Idaho, the ores resemble those of Montana in that a high-grade. concentrate can be made; but the silver is usually lower and the lead somewhat higher.

It is in Colorado that the typically difficult-to-concentrate complex ore is found. These ores, disregarding the carbonates which are of secondary origin as distinguished from the primary sulphides, have a variety of structure and of minerals that rarely occur in any of the other important districts. The percentage of iron is invariably high and this undesirable element is present not only as pyrite difficult to separate-but as a constituent of the black jack which, for the most part, contains only 45 to 50 per cent, and frequently less, zinc. Gold, silver, lead, or copper are generally present, sometimes all together.

The essential differences between these more important districts are roughly outlined in the above summary. A more detailed description including many of the zinc-producing regions has been prepared but, on account of its length, can not be presented here and will be found in the auxiliary files of this Commission. Many of the districts present no markedly unusual features and zinc mining is quite similar to other mining operations in those districts. A fuller treatment of the industry in the Joplin area, which presents some characteristic features, will be found under separate title in the second section of this report.

Total.

327,712 345, 260 378, 816 406, 416 406, 959 586, 491 701,995 710,972

627, 100

1 Estimated.

RELATION OF DOMESTIC PRODUCTION TO DOMESTIC CONSUMPTION.

The following statistics do not include the ore consumed by producers of zinc oxide or manufacturers of electrolytic zinc, and represent, therefore, only the receipts of zinc ore by smelters. Exports of ore are also not included. The data for imports do not correspond with the figures of the Department of Commerce. They are reported by the smelters, in the case of bonded smelting, when the spelter leaves their works while the Government reports date from the time the spelter is entered for export at the customhouse. The difference in periods covered by the two sets of reports accounts in part for the discrepancies.

5 In addition to the ore reported from Canada and Mexico, smelters received a few thousand tons of ore from Europe and Eastern Siberia in 1913.

Since the greater part of the ore produced in the United States goes into the production of spelter by retort smelting, the above figures represent closely the ratio of domestic to foreign ores. The most important corrections are those for electrolytic spelter production and the zinc ore used directly in the making of pigments. This will amount to something like 200,000 tons annually.

The average grade of the zinc ore smelted in the United States was 51 per cent in 1918, 49.9 per cent in 1917, 46.2 per cent in 1916, 50.1 per cent in 1915, and 48.8 per cent in 1914. There are no data to show what proportion of this was crude ore that was sold without mechanical concentration, but most of it is known to be a concentrated product. An interesting feature is the amount of "calamine" (including under this term all oxide ores except those of Franklin, N. J.). Since these ores are invariably lower grade than blende, their relative proportion of the total product has a marked effect on the average grade. The only data are those furnished by smelters and covering their con-sumption. In 1914 the calamine smelted was about 26 per cent of the total; in 1915 it was about 28.5 per cent; in 1916, about 294 per cent; in 1917, 26.9 per cent; and in 1918, about 22.4. The tendency to use a larger proportion of calamine that was exhibited in 1915 and 1916 (because of small roasting capacity in the new plants) was checked in 1917 when the smelters were forced by adverse market conditions to seek higher grade ore and in 1918 the relative use of calamine diminished further.

1 These data are published by W. R. Ingalls in the Engineering and Mining Journal. 128898-19-3