Iron Ore The chief iron ore regions of the United States are usually classi fied by the United States Geological Survey as shown in the following table, which gives for 1915 the proportion of our total production credited to each.
Lake Su w region 83.4 per cent Birmingham district, istrict, Alabama 8.5 per cent Clusttanzoga district. Tennessee 1 0 per cent Adirori k district. New York 1.3 per cent New Jersey and South New York 1.2 per cent Other districts 4.6 per cent The Lake Superior region is in turn divided into several ranges, and their proportion of the total Lake Superior production is tabulated below.
Marquette range. Northern Michigan 8 per cent Menominee range, Michigan and Wisconsin 10 per cent ()enable range, Michigan and Wisconsin 11 per cent Vermilion range, Northern Minnesota 3 per cent Mesabi range, Northern Minnesota 66 per cent Cuyuna range, Northern Minnesota 2 per cent In the year 1915 there was taken from the Mesabi range 33,802,409 tons of ore— an in crease of 56 per cent over the 1914 yield; an amount equal to 66 per cent of the yield of the whole Lake Superior region, and 55 per cent of the entire yield of the United States. The Menominee range yielded 4,665,465 tons, an in crease of 27 per cent over 1914. The Gogebic range yielded 4,996,237 tons —9 per cent in crease; the Marquette, 3,817,892 tons-15 per cent increase; the Vermilion, 1,541,645 tons — 13 per cent increase; the Cuyuna, 1,120,606 tons —44 per cent increase. The total yield of the Lake Superior region for 1915 was 46,944,254 tons-84.54 per cent of the year's yield for the whole United States. The record production of individual mines surpass any in the world. In 1915 the Mahoning mine, at Hibbing, Minn., took first place with an output of Z311,940 gross tons. The Hull-Rust mine, adjoining the Ma honing, stood second, with 2,307,195 tons. The Red Mountain mines at Bessemer, Ala., which stood first in 1914, was third, with 2,138,015 tons. The Individual records of 167 of the principal mines in the United States are to be found on pages 287-289 of • The Mineral Re sources of the United States: Part In for 1915, published by the United States Geological Sur vey, in 1917.
In the South there are three important iron mining centres—one near Birmingham, Ala., another in southeastern Tennessee, and the third in southwestern Virginia. The ores are red hematites and low-grade limonites. The growth of the Alabama industry is due to cheap ore, limestone and cooking-coal being found in close proximity. Pennsylvania produces some limonite. Of the western States, Colorado pro duces limonite, and in Utah and Wyoming are great deposits of magnetite and hematite, des tined to he of importance in the future. The famous specular hematite mines at Pilot Knob and Iron Mountain, Mo., are practically ex hausted. Texas has large deposits of ore, and several other States are or will be important producers. Various estimates of the apparent resetves of iron ore in the United States range from 5,200,000,000 tons to 7,550,000,000 tons. This supply is being drawn on to the extent of about 55,000,000 tons a year. Besides the great production of its own mines the United States imports annually a considerable quantity of foreign ores. In 1915 this importation amounted to 4,344,281 gross tons, valued at $4,181,645. Of
this, 831,618 tons came from Cuba; 204,632 tons from Sweden; 153,600 tons from Chile; 84,124 tons from Canada; 42,092 tons from Spain; and 21,825 tons from French Africa. The exports of the United States for the same year were 707,641 gross tons, valued at $2,181,629.
Mining and Handling Iron Some extraordinary records of cheap mining and transportation have been made in the Lake Su perior iron-ore trade. Large ore-bodies, effi cient labor, and excellent management have been the factors in reducing mining costs, while the long lake-water haul, nearly 900 miles, in specially designed vessels, has made it possible to put down Lake Superior ores at Pittsburg, over 1,100 miles from the mine, at a total trans portation cost of under $2 per ton. On the Mesabi range, in some large mines steam shovels load the ore directly upon the cars, one shovel having loaded 170,000 tons in 26 days, or at the rate of over 6,500 tons per day. The shovels are each operated by five men, and the labor cost for mining and loading averages but about 16c per tons, and at one mine which dug and loaded 293,651 tons in 174 days, the labor cost was only 4c per ton. The loaded ore-trains go 50 to 115 miles to a shipping port. There they are run on to long, high docks hav ing large pockets or bins into which the ore runs through openings in the bottom of the cars. From these pockets the ore passes by gravity down along chutes into the hold of the vessel, so that no hand-labor is required. The ore pockets hold about 160 tons each, and number from 90 to 384, according to the length of the dock.
In unloading the ore from the vessels the use of labor-saving machinery is even more notable. A series of steel bridges, easily moved along the docks, is supplied with hinged arms which can be lowered into the hatch of the ves sel. Along each arm and across the bridge runs a trolley-train to which are attached automatic grabs similar to a double scoop. The grab or holds about five tons of ore, and when it begins to draw together it digs into the ore. The grabs can remove over half of the cargo without any assistance, and the remaining half is brought directly under the hatch by use of a scraper, operated by similar machinery. The grabs are so controlled by the engineer that he can drop them at any point over the hold he may wish, and after a grab seizes its load of ore it is raised at full speed, carried rapidly along the trolley to any given point, and dumped into railroad cars or on stock piles. This 5-ton grab has a hoisting speed of 100 feet a minute, and can run along the bridge at the rate of 1,000 feet a minute. The bridges to which the arms with their grabs are attached are worked by electricity. By such a device 26 men can do the work of 300 under the old system. Another unloading device, the Hulett unloader requires even fewer men and takes out a larger proportion of the cargo without aid.
See GOETHITE ; HEMATITE; ILMENITE ; LIMO NITE; MAGNETITE; MINING; ORE DEPOSITS.
Consult Eckel, C. E., 'Iron Ores' (New York 1914) ' • 'The Mineral Industry' (annually New York); and files of the Engineering and Min ing Journal and Engineering Record (monthly New York).