Glossary

Hematite is a naturally occurring iron oxide mineral with the chemical formula Fe₂O₃, and it is one of the primary ores of iron used in steelmaking. It contains about 70% iron by weight, making it one of the richest and most important sources of iron on Earth.

Hematite forms in both metallic and earthy varieties, depending on how it crystallizes. In its pure, crystalline form, it appears as a dark steel-gray or black mineral with a metallic luster, often showing a slight red tint on its edges. In its more common earthy form, it appears as a reddish-brown, dull powdery material—this variety is sometimes called red ochre and has been used as a pigment since prehistoric times. Regardless of appearance, hematite always leaves a reddish-brown streak when scratched on a surface, which is one of its most distinctive identifying features.

Hematite forms under a wide range of geological conditions. It can develop through precipitation from water, oxidation of other iron minerals (like magnetite), or as a weathering product of iron-rich rocks. It is commonly found in sedimentary deposits, banded iron formations, and metamorphic and igneous environments. Major hematite deposits are found in Brazil, Australia, China, India, Russia, and the United States—notably in the Lake Superior region, which has supplied iron ore for over a century.

In industrial use, hematite is primarily mined, crushed, and smelted in a blast furnace, where it is reduced by carbon (in the form of coke) to produce pig iron, which is then refined into steel. The reaction removes oxygen from the Fe₂O₃ molecule, leaving behind metallic iron.

Beyond metallurgy, hematite has several secondary uses. Finely ground hematite is used as a pigment for paints and cosmetics due to its rich red color. It is also used as a radiation shielding material, in heavy concrete, and as a polishing compound. Because of its magnetic properties when heated, it has also found uses in scientific instruments and electronics.