CHAPTER VIII
Iron Ore, Preparation and Smelting
155. Iron Ore.—An ore is a portion of the earth’s substance containing metal for which it is mined and worked; the class to which it belongs depends upon the amount and variety of the metal it contains. Any ore that is to be used for the extraction of a certain metal must contain the metal in sufficient amounts to make the operation profitable.
Iron, ordinarily, does not occur in a native state or in a condition suitable for use in the arts and manufactures. The iron in meteors, frequently called native iron, is the nearest possible approach to it. Meteorites, commonly known as falling stones or shooting stars, are solid masses that have fallen from high regions of the atmosphere and are only occasionally found in different parts of the world. They are considered more valuable as a curiosity than as material for manufacturing purposes. The metallurgist, chemist, or geologist can readily distinguish them from other masses, because they invariably contain considerable nickel, which seldom appears in any of the ordinary iron ores. They are usually found in a mass containing crystals and are nearly always covered with a thin coating of oxide, which protects the metal from further oxidation. Several large meteors have been found, one in Germany weighing 3300 pounds and a larger one in Greenland weighing 49,000 pounds. The largest one known was discovered by Lieutenant Peary in the Arctic regions. It weighs 75,000 pounds. He brought it to New York City, where it can now be seen at the American Museum of Natural History.
Pure iron is obtainable only as a chemical, and as such it is used in the preparation of medicines. As a commercial product, such as is used in the arts and manufactures and by the smith, it is always combined with other substances, such as carbon, silicon, and phosphorus.
Iron is distributed through the earth very widely, but not always in sufficient quantities to make its extraction from the ore profitable; consequently the ores used for the extraction of iron are somewhat limited. There are four general grades of iron ore, which are known by the following names: magnetite, red hematite, limonite, and ferrous carbonate. These are subdivided and classified according to the particular composition of each.
156. Magnetite when pure contains about 72 per cent of iron, and so is the richest ore used in the manufactures. It is black, brittle, and generally magnetic, and leaves a black streak when drawn across a piece of unglazed porcelain. It sometimes occurs in crystals or in a granular condition like sand, but generally in a massive form. It is found principally in a belt running along the eastern coast of the United States, from Lake Champlain to South Carolina. There are considerable quantities of it in New Jersey and eastern Pennsylvania, but the greatest deposits are found in Missouri and northern Michigan; some is mined also in eastern Canada. It is a valuable ore in Sweden.
A mineral known as franklinite, which is closely allied to magnetite, is a mixture of magnetite and oxides of manganese and zinc. In appearance it resembles magnetite, but is less magnetic. In New Jersey, where it is found quite abundantly, it is treated for the extraction of the zinc, and the residue thus obtained is used for the manufacture of spiegeleisen, which is an iron containing a large amount of manganese, usually from 8 to 25 per cent.
157. Red hematite is found in earthy and compact forms. It varies in color from a deep red to a steel gray, but all varieties leave a red streak on unglazed porcelain. It is found also in a number of shapes or varieties, such as crystalline, columnar, fibrous, and masses of irregular form. Special names have been given to these. The brilliant crystalline variety is known as specular ore, the scaly foliated kind as micaceous ore, and the earthy one as red ocher. Each one of this class contains about 70 per cent of iron, and on account of the abundance, the comparative freedom from injurious ingredients, and the quality of iron it produces, it is considered the most important of all the ores in the United States.
Until the discovery of large deposits of this ore in the Lake Superior district it was chiefly obtained from a belt extending along the eastern coast of the United States just west of the magnetite deposits and ending in Alabama. Some of this ore is found in New York, but there is not a great amount of it north of Danville, Pennsylvania. At present the greatest quantities that are used come from the Lake Superior district. There, ore of almost any desired composition may be obtained, and the enormous quantities, the purity, the small cost of mining, and the excellent shipping facilities have made it the greatest ore-producing section of the United States.