Iron, in the forms of wrought iron, cast iron, and different kinds of steel, is used in the industries and trades more than any other metal. All forms of iron arc obtained from the earth and are found combined in different amounts with other elements and substances which can be separated only by strong heat. In addition to being found as a compound, iron is mixed in all proportions with rock, dirt, etc.
The most common forms of iron ores are as follows: Magnetite or lodestone (symbol Fe 3O 4), the richest of all iron ores, possesses the property of attracting to itself small pieces of iron.
Hematite (symbol Fe2 O3), the next richest ore, is very abundant in this country.
Limonite (2Fe203. 3H1O), sometimes called bog-iron ore, is not a pure oxide and is known by the yellow streak it produces on porcelain. Siderite (FeCO3), called spathic iron ore, contains about 48% of iron.