The Pros of Magnetite Vs. Hematite for Extraction of Iron

For both magnetite and hematite, iron extraction commonly occurs within a blast furnace.

The worldwide mining industry extracts iron from both hematite and magnetite ores. Hematite is a direct shipping ore whose naturally high iron content makes it an ideal choice for extraction. In contrast, magnetite tends to contain lower levels of iron, resulting in a need to concentrate the iron content, complicating the extraction process. Nevertheless, magnetite offers some significant advantages over hematite for the extraction of iron.

Magnetism

After extraction, the ore must undergo beneficiation. Beneficiation is a broad term that refers to several different processes used by miners to remove any impurities and concentrate the iron. According to the Environmental Protection Agency, the most common beneficiation process is magnetic separation, which is used on over 90 percent of the iron extracted in the United States Magnetic separation removes non-magnetic impurities from magnetic ore uses magnetic forces. Magnetite is naturally a very magnetic metal and is ideally suited for magnetic separation. However, hematite is only weakly magnetic, a factor making magnetic separation inefficient. As of 2008, the Bureau of Mines dubbed the magnetic separation of hematite "uneconomic." Magnetite's natural magnetic qualities offer one distinct financial advantage over the use of hematite for iron extraction.

Concentration

In his presentation, "What You Need To Know About The Beneficiation Of Low Iron Grade Ores," Sean O'Donnell notes that direct shipping hematite ore contains between 58 and 65 percent iron. Magnetite naturally contains between 20 and 30 percent iron. However, after concentration, magnetite will contain more iron than even hematite, with expected concentrations ranging between 68 and 70 percent. Therefore, the potential for higher concentrations of iron is another reason to prefer magnetite over hematite for iron extraction.

Impurities

When compared to hematite, concentrated magnetite tends to contain lower quantities of impurities. Hematite often contains significant amounts of silica, phosphorus, sulfur, alumina and manganese oxides. The presence of these impurities in hematite deposits can significantly increase the cost of iron extraction and beneficiation. Concentrated magnetite contains few impurities and is particularly low in alumina, manganese oxides and phosphorus. Since impurities can be costly to remove, magnetite's fewer impurities offer another reason to prefer it over hematite.

Availability

The world's supply of hematite deposits are rapidly diminishing, due to the popularity of hematite for iron extraction. In 2008, three major members of the mining industry, Asia Iron Holdings Ltd, Atlas Iron Ltd, and Gindalbie Metals Ltd, also issued a joint statement explaining that the world's hematite supply was unable to keep up with the growing demand for steel in rapidly industrializing nations such as China and India. With hematite unable to meet world demand, magnetite provides a viable alternative.

References

• Asia Iron Holdings Limited Atlas Iron Limited Gindalbie Metals Limited; Joint response to the Carbon Pollution Reduction Scheme Green Paper July 2008
• EPA; Extraction and beneficiation of ores and minerals, Volume 3 Iron
• Sean O'Donnell; What You Need To Know About The Beneficiation Of Low iron grade ores

Resources

• U.S. Department of Energy; Energy and Environmental Profile of the U.S. Mining Industry, Iron