Types of hematite:
Iron (Fe) is one of the most abundant rock-forming elements, constituting about 5% of the Earth’s crust. It is the fourth most abundant element after oxygen, silicon and aluminum and, after aluminum, the most abundant and widely distributed metal. Iron is indispensable to modern civilization and people have been skilled in its use for more than 3,000 years. However, its use only became widespread in the 14th century, when smelting furnaces (the forerunner of blast furnaces) began to replace forges.
Iron ores are rocks from which metallic iron can be economically extracted. These rocks are usually found in the form of hematite (Fe2O3) or magnetite (Fe3O4). About 98% of world iron ore production is used to make iron in the form of steel.
Physical Properties of Hematite
Hematite has an extremely variable appearance. Its luster can range from earthy to submetallic to metallic. Its color ranges include red to brown and black to gray to silver. It occurs in many forms that include micaceous, massive, crystalline, botryoidal, fibrous, oolitic, and others.
Even though hematite has a highly variable appearance, it always produces a reddish streak. Students in introductory geology courses are usually surprised to see a silver-colored mineral produce a reddish streak. They quickly learn that the reddish streak is the most important clue for identifying hematite.
Hematite is not magnetic and should not respond to a common magnet. However, many specimens of hematite contain enough magnetite that they are attracted to a common magnet. This can lead to an incorrect assumption that the specimen is magnetite or the weakly magnetic pyrrhotite. The investigator must check other properties to make a proper identification.
If the investigator checks the streak, a reddish streak will rule out identification as magnetite or pyrrhotite. Instead, if the specimen is magnetic and has a reddish streak, it is most likely a combination of hematite and magnetite.
Uses of Hematite (Healing Stone)
Some people believe that carrying pieces of tumble-polished hematite, known as “healing stones,” will bring relief from certain medical problems. There is no scientific proof that this use of hematite has any positive effect beyond being a placebo. Using hematite as a “healing stone” or a “healing crystal” can actually be harmful because it diverts people from seeing a doctor who can provide proper care. Then when the person with the problem finally decides to see a doctor, their situation is more severe.
Iron Furnace: In the 1700s and 1800s, small mines in the eastern United States produced hematite which served as the primary iron ore of the region. The ore was processed by heating it by burning charcoal in simple stone furnaces. The iron ore deposits were small and difficult to exploit. When the large iron ore deposits of the Great Lakes region were discovered, iron ore was no longer mined in the eastern United States. Shown is the Vesuvius Iron Furnace of southern Ohio. USGS photo.
Other Uses of Hematite
Hematite is used for a number of other purposes. It is a very dense and inexpensive material that is effective at stopping x-rays. For that reason it is used for radiation shielding around medical and scientific equipment. The low cost and high density of hematite and other iron ores also makes them useful as ballast for ships.
Hematite can also be ground to a fine powder that when mixed with water will make a liquid with a very high specific gravity. These liquids are used in the “float-sink” processing of coal and other mineral material. The crushed coal, which has a very low specific gravity, is placed on the heavy liquid and the light clean coal floats, while high-specific-gravity impurities such as pyrite sink.
Finally, hematite is the material used to make polishing compounds known as “red rouge” and “jeweler’s rouge.” Red rouge is a hematite powder used to polish brass and other soft metals. It can be added to crushed corn cob media or crushed walnut shell media for tumble-polishing brass shell casings. Jeweler’s rouge is a paste used on a soft cloth to polish gold and silver jewelry.