Hematite

Hematite, mineral and the most abundant ore of iron, composed of ferric oxide, Fe₂O₃. It is widely distributed over the world, occurring in rocks of all ages. In the United States hematite makes up about 50 percent of all the iron ore mined. The chief iron-ore districts in the U.S., and probably the most important hematite regions in the world, are located along the shores of Lake Superior in Michigan, Wisconsin, and Minnesota. Extensive deposits are also found in the Appalachian region extending from New York to Alabama, with particularly noteworthy deposits in eastern Tennessee and northern Alabama.

Hematite occurs in rhombohedral crystals (see Crystal), called specular iron in massive formations, and in earthy forms, called red ocher. The crystals are translucent, range in color from dark gray to black, and have a brilliant metallic luster; the earthy varieties are lusterless and red. The hardness ranges from 5.5 to 6.5 and the specific gravity from 4.2 to 5.25.

In addition to being the principal ore of iron, hematite is a constituent of a number of abrasives and pigments.