# The American Cyclopædia (1879)/Iron Ores

IRON ORES. The term iron ore is limited to oxides of iron, either as such or in combination with water or carbonic acid. Other compounds of iron, as for example the sulphide, are not adapted for iron making. The term is further limited to deposits of sufficient purity and richness to render smelting profitable. These factors differ in different localities. Both the ferric and magnetic oxides occur in nature, sometimes nearly pure; they are called respectively hematite (red or anhydrous hematite) and magnetite. Ferric oxide also occurs in combination with water in various definite proportions; these compounds are called hydrous or brown hematites. Ferrous oxide is a component of many minerals, but only the ferrous carbonate is important as an ore of iron; it is known as spathic ore. Mineralogically iron ores may be grouped as follows:

 ORES. Formula. Crystalline form. Hardness. Specific gravity. Color of powder. Per ct. metallic iron. Water. Carbonic acid. Ferric Oxide—Red hematite. Hematite Fe₂O₂ Hexagonal 5.6-6.5 4.5-5.3 Cherry red to reddish brown 70.00 . . . . . . . . Ferric Oxide Hydrated—Brown hematite. Limonite Fe₂O₂,3H₂O Massive 5.5-5 3.6-4 .mw-parser-output .nowrap,.mw-parser-output .nowrap a:before,.mw-parser-output .nowrap .selflink:before{white-space:nowrap} Yellowish brown to rusty yellow 52.34 25.23 . . . . Xanthosiderite Fe₂O₂,2H₂O Massive or fibrous 2.5 . . . . Ochre yellow 57.14 18.37 . . . . Limonite 2Fe₂O₂,3H₂O Massive or earthy 5-5.5 3.6-4 Yellowish brown 59.90 14.43 . . . . Göthite FeO,CO₂ Orthorhombic 5-5.5 4-4.4 Brownish to ochre yellow 63.03 10.11 . . . . Turgite Fe₂O₂,H₂O Massive 5-6 3.5-3.7 Reddish 66.28 5.33 . . . . Ferrous Carbonate—Spathic Ore. Siderite 2Fe₂O₂,H₂O Hexagonal 3.5-4.5 3.7-3.9 White 48.27 . . . . 37.93 Magnetic Oxide—Magnetite. Magnetite Fe₂O₄ Isometric 5.5-6.5 4.9-5.2 Black 72.41 . . . . . . . .

CONSTITUENTS.  HEMATITES. HYDROUS HEMATITES. CARBONATES. MAGNETITES.

SPATHIC ORE. EARTHY CARBONATES. BLACKSAND.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Ferrous oxide . . . .    2.34    1.670 . . . . . . . . . . . . . . . .  46.22   4.69   43.84  46.43  35.14   39.92  45.27   37.07  41.45 7.704   27.55  23.56 . . . . . . . . . . . .
Ferric oxide  90.55   91.45   90.87   70.380   76.87  47.49   81.55 . . . .  67.22    0.81 . . . .   7.62    3.60   0.64 . . . . . . . . 54.715    58.93  52.44 . . . . . . . . . . . .
Magnetic oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.25  94.20   79.78
Manganous oxide    0.10 . . . . . . . . . . . . . . . . . . . . . . . .  10.55 . . . .   12.64   1.44   0.50    0.95 . . . .    0.23 . . . . . . . .    0.10  10.40 . . . . . . . . . . . .
Manganic oxide . . . . . . . . . . . .    4.005 . . . .   4.32    0.10 . . . .   3.36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.934 . . . . . . . . . . . . . . . .    0.28
Silica   7.05    3.99    5.18    9.185    0.71  26.70    4.53   1.08  12.49 . . . .  10.29  21.91    8.76  11.24    2.70   3.02 20.532    12.54   3.10 4.32  5.10    0.75
Alumina   1.43    1.40    0.89    1.232 . . . .   7.34    1.49 . . . .   2.49 . . . .   4.80   2.67    7.86   8.14 . . . .   1.33 4.034    0.29   2.05 0.28 . . . .    4.62
Lime   0.71    0.51    1.76    0.880 . . . .   1.67 trace   0.75   1.25    0.28   0.76   3.64    7.44   1.72    6.61 . . . . 4.643    0.38   1.20 0.14 . . . .    0.13
Magnesia   0.06    0.22    0.13    0.211 . . . .   0.25    0.47   2.73   4.11    3.63   0.94   0.08    3.82   1.51    7.40   0.89 2.222    0.61   1.05 . . . . . . . .    2.04
Alkalies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   0.24    0.27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Water (ignition)  . . . . . . . . . . . .   13.797   19.25   8.90   11.70   0.09 . . . . . . . .   1.38   2.05    2.97   0.03 . . . .   0.18 1.418    0.11 . . . . 0.38 . . . . . . . .
Organic matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   1.14 . . . . . . . .   0.95    9.80  23.58 2.941 . . . . . . . . . . . . . . . . . . . .
Carbonic acid . . . . . . . . . . . . . . . . . . . . . . . . . . . .  38.38   3.35   38.86  30.44  24.05   22.85  30.32   36.14  28.06 0.760    0.12   6.10 . . . . . . . . . . . .
Phosphoric acid  trace    0.141    0.069    0.310    0.10   2.67    0.16 . . . . trace . . . .   0.74 trace    1.86   0.17    0.23 not det. 0.719 trace   0.009 0.87  0.50 . . . .
Sulphuric acid . . . . . . . . . . . . . . . .    3.10 . . . . . . . . . . . .   0.49 . . . . trace   0.42 . . . . . . . . . . . .   0.006 0.498 . . . . . . . . Titanic acid.   12.08
Sulphur   0.03 . . . .    0.078 trace . . . .   0.24 . . . . . . . . . . . . . . . .   0.04 . . . .    0.11 trace . . . .   0.040
 ${\displaystyle \scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}}$ FeS₂ ${\displaystyle \scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}}$ 0.143
0.04 . . . .
 ${\displaystyle \scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}}$ Chromic oxide with ${\displaystyle \scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}}$ trace of vanadium.
0.32

99.93   100.051   100.647   100.000   100.03   99.58   100.00   99.80   99.45   100.06   98.40   98.32   100.41   99.99   100.18   98.556  101.263    100.67   99.909  100.24   99.80  100.00

—The distribution of the iron ores of the United States, with relation to the resources of the country in mineral fuel, has been well stated in the “Report on Iron and Steel” of Mr. Abram S. Hewitt, United States commissioner to the Paris exposition of 1867, as follows: “The position of the coal measures of the United States suggests the idea of a gigantic bowl filled with treasure, the outer rim of which skirts along the Atlantic to the gulf of Mexico, and thence returning by the plains which lie at the eastern base of the Rocky mountains, passes by the great lakes to the place of beginning, on the borders of Pennsylvania and New York. The rim of this basin is filled with exhaustless stores of iron ore of every variety, and of the best quality. In seeking the natural channels of water communication, whether on the north, east, south, or west, the coal must cut this metalliferous rim, and in turn the iron ores may be carried back to the coal, to be used in conjunction with the carboniferous ores, which are quite as abundant in the United States as they are in England, but hitherto have been left unwrought, in consequence of the cheaper rate of procuring the richer ores from the rim of the basin. Along the Atlantic slope, in the highland range from the borders of the Hudson river to the state of Georgia, a distance of 1,000 miles, is found the great magnetic range, traversing seven entire states in its length and course. Parallel with this, in the great limestone valley, which lies along the margin of the coal field, are the brown hematites, in such quantities at some points, especially in Virginia, Tennessee, and Alabama, as fairly to stagger the imagination. And finally, in the coal basin is a stratum of fossiliferous ore, beginning in a comparatively thin seam in the state of New York, and terminating in the state of Alabama, in a bed of 15 feet in thickness, over which the horseman may ride for more than 100 miles. Beneath this bed, but still above water level, are to be found the coal seams, exposed upon mountain sides, whose flanks are covered with magnificent timber, available either for mining purposes or the manufacture of charcoal iron. Passing westward, in Arkansas and Missouri is reached that wonderful range of red oxide of iron, which, in mountains rising hundreds of feet above the surface, or in beds beneath the soil, culminates at Lake Superior in deposits of ore which excite the wonder of all beholders; and returning thence to the Atlantic slope, in the Adirondacks of New York, is a vast undeveloped region, watered by rivers whose beds are of iron, and traversed by mountains whose foundations are laid upon the same material; while in and among the coal beds themselves are found scattered deposits of hematite and fossiliferous ores, which, by their close proximity to the coal, have inaugurated the iron industry of our day. From these vast treasures the world may draw its supply for centuries to come, and with these the inquirer may rest contented, without further question; for all the coal of the rest of the world might be deposited within this iron rim, and its square miles would not occupy one quarter of the coal area of the United States.” The table on the preceding page gives analyses of various ores from different localities, indicated by numbers as follows: A. Hematites. 1. Whitehaven, Cumberland, England. 2. Iron mountain, Missouri; specular ore from vein. (The phosphoric acid is the average of four determinations in as many samples, varying from 0.252 to 0.081 per cent.) 3. Pilot Knob, Missouri; specular ore from main ore bed. B. Hydrous Hematites. 4. Lake ore, Sweden. (Phosphoric acid varies from 0.051 to 1.213 per cent.) 5. Katahdin furnace, Piscataquis co., Me., resulting from the decomposition of iron pyrites. 6. Silicious ore, York co., Pa. 7. Pennsylvania furnace ore-bank, Centre co., Pa. C. Carbonates. I. Spathic ore. 8. Müsner Stahlberg, Prussia. 9. Calcined spathic ore from Altenberg, Styria, used for Bessemer process at Neuberg. 10. Brendon hill, Somersetshire, England. II. Earthy carbonates. 11. Gubbin ironstone, Dudley, S. Staffordshire, England. 12. Sphærosiderite from Ahaus, Prussia. 13. Eston, Cleveland, England; main seam. 14. Carbonate ore from Fayette co., Pa. III. Blackband. 15. Shelton, N. Staffordshire, England. 16. Westphalian blackband, low grade. 17. Best Westphalian, roasted. D. Magnetites. 18. Dannemora ore, Sweden. 19. Granrot ore, Sweden. 20. Lake Champlain, “new bed” ore, unusually free from apatite. 21. A sample from New Hope mine, Morris co., N. J. (The ores in northern New Jersey are very variable in regard to silica and phosphoric acid. The former varies from 2 to 40 per cent., the latter from 0 to 3 per cent. Low percentages of both silica and phosphoric acid, and freedom from sulphur, are usual.) 22. Titaniferous, from Greensboro, N. C. The following table shows the amount of sulphur and phosphorus contained in most of the Swedish and in some of the Prussian ores:

 LOCALITIES AND ORES. Sulphur,  per cent. Phosphorus, per cent. Rastelp, Sweden, magnetite 0.011 0.0006 Pershyttan, Sweden, magnetite 0.007 0.0130 Lerberg, Sweden, magnetite trace. 0.0013 Marnäs, Sweden, magnetite . . . . 0.0070 Hilläng, Sweden, magnetite 0.02 0.0050 Prague, Byberg, and Nyberg, Sweden, magnetite 0.081 0.0170 Färola, Sweden, magnetite 0.06 0.0100 Nartorp, Sweden, magnetite 0.07 0.0160 Stenebo, Sweden, magnetite 0.09 0.0300 Dannemora, Sweden, magnetite 0.037 0.0060 Near Wiesbaden, Prussia, red hematite trace. 0.310 Near Coblentz, Prussia, red hematite trace. 0.210 Near Coblentz, Prussia, brown hematite 0.08 0.150 Near Wiesbaden, Prussia, brown hematite trace. 0.210 Limburg, Prussia, spathic ore 0.60 0.017 Oberlahn, Prussia, spathic ore 0.32 0.012 Werbenbach, Prussia, spathic ore 0.564 0.010 Westphalia, Prussia, blackband 0.020 0.360 Rhine Province, Prussia, brown hematite . . . . 0.090 Westphalia, Prussia, brown hematite . . . . 0.042

Treatment of Ores. Iron ores are generally used in the blast furnace in the condition in which they are mined, but sometimes they are submitted to a preliminary treatment. The carbonate ores are invariably roasted before smelting. This drives off the carbonic acid; the ferrous is converted into magnetic oxide; and the ore is rendered not only richer but much more porous, and thereby more readily reduced. Ores containing much sulphur are also roasted with access of air, and the greater part of the sulphur is driven off as sulphurous acid. Heavy compact ores are occasionally roasted to render them friable. Roasting may be effected in open heaps or within brick walls by piling the ore and fuel (wood or brush) in layers, and allowing it to burn out. This method is far less thorough and efficient than roasting in shaft furnaces. In the latter case the fuel (small coal) and ore may be charged alternately, or gas (from the blast furnace or suitable generators) may be used. The operation is continuous. Brown hematites often occur mixed largely with clay and other earthy matters; they are then submitted to a dressing or concentrating process by washing, in which the lighter clay is washed off and the heavier ore remains.—Forge and mill cinders, produced in puddling and heating iron, are very rich in iron, containing from 40 to 75 per cent. Although, strictly speaking, they are not ores of iron, yet they are used for reduction in the blast furnace. Their use in large quantity is attended with disadvantage, owing to the facility with which they melt and escape reduction. Puddling cinder, moreover, contains the greater part of the impurities of the iron from which it is made, and yields therefore inferior iron. Roasting renders the cinder more infusible, and also effects a partial purification.