Hematite is a mineral with diverse applications, ranging from being the world’s most important source of iron to its use in fine jewelry. It is an iron oxide (\(\text{Fe}_2\text{O}_3\)), a compound of iron and oxygen. Its name comes from the Greek word haimatitis, meaning “blood-red,” a reference to the vivid red color of its streak or powdered form. This red powder is the defining characteristic of hematite, even when the solid mineral appears steel-gray or black.
The Main Source of Iron Ore
Hematite is the primary ore for producing iron, making it the most economically significant mineral globally. It is the foundation of the steel industry, which supports modern infrastructure and manufacturing. Pure hematite contains up to 70% iron by weight, a concentration that makes it highly desirable for mining operations.
The vast majority of hematite is extracted through large-scale open-pit mining operations in massive sedimentary deposits known as banded iron formations. These deposits are exceptionally large, such as those found in Australia, Brazil, and the Lake Superior district in North America. The high iron concentration in hematite ore means that it often requires less complex processing, frequently called “direct-shipping ore,” before being smelted.
Although the mineral magnetite has a slightly higher theoretical iron content, hematite is the leading source because it is found in much higher concentrations within mineable ore bodies. Hematite ore contains a high enough percentage of iron to be used directly after simple crushing and screening. Magnetite ore, by contrast, requires an energy-intensive concentration process to upgrade the iron content before it is suitable for steel production.
The scale of hematite mining is enormous, with some of the largest mines in the world extracting over 100 million tons of ore annually. This raw material is crucial for creating pig iron, which is then refined into steel for everything from automobiles and appliances to skyscrapers and bridges.
Pigments and Polishing Compounds
When hematite is ground into a fine powder, its vibrant red streak is revealed, leading to its historical and modern use as a pigment. This powdered form is widely known as red ochre, a coloring agent used by humans for tens of thousands of years. Ancient civilizations used red ochre in cave paintings, ceramics, and for personal body decoration.
The color produced by hematite is stable and enduring, making it a reliable pigment for modern paints, glazes, and industrial coatings. It is responsible for the traditional color of red chalk drawings and contributes to the inexpensive red paint used on classic structures like barns.
A purer, more refined form of this powdered hematite is known commercially as “jeweler’s rouge” or “red rouge.” This mild abrasive is used specifically for polishing fine metals like gold, silver, and brass. Hematite has a moderate hardness, between 5.5 and 6.5 on the Mohs scale, which allows the fine powder to remove microscopic scratches and impart a brilliant, non-scratching luster.
Use in Jewelry and Ornamental Stone
Beyond its industrial applications, solid hematite is valued in the lapidary arts for its unique aesthetic properties. When polished, the mineral often displays a striking, high metallic luster and a dark, gunmetal-gray to nearly black color. This appearance gives finished pieces a substantial, weighty, and sophisticated look.
Lapidaries frequently cut hematite into cabochons, beads, and small sculptures. Its hardness is sufficient to hold a polish, although it is brittle and requires careful handling, especially in jewelry settings. The mineral’s uniform texture also makes it suitable for detailed carvings, such as intaglios and cameos, where the dark color provides a strong contrast.
The stone’s density contributes to the weighty feel of hematite jewelry, making it a popular choice for necklaces and bracelets. The highly polished metallic look of some varieties of hematite is sometimes confused with the naturally magnetic mineral magnetite.
Applications Based on Density
A specialized set of applications leverages hematite’s high specific gravity, or density, which ranges from 5.0 to 5.3 grams per cubic centimeter. This density is significantly higher than most common minerals and aggregates, making it exceptionally heavy for its volume. This characteristic is utilized in processes where heavy material is required for weight or separation.
One such use is as a form of ballast, where the bulk material is used to provide stability or anchoring weight. For example, hematite can be used as heavy aggregate in the construction of pipelines or as a stabilizing weight in the hulls of ships. The high density also makes it a preferred aggregate for producing high-density concrete.
This dense concrete is particularly effective for radiation shielding in medical facilities or nuclear installations, where a heavy barrier is necessary to block harmful rays. Furthermore, finely ground hematite powder can be suspended in liquid to create a high-density medium for mineral processing. This technique, known as heavy media separation, allows for the efficient separation of minerals based on their differing densities.