What is Iron Oxide?

Desi C.

Iron oxide is any one of a range of chemical compounds made up of iron and oxygen. Most of these are naturally occurring; some form in the soil or in chemical deposits in rocks or mountains, and rust is also a very common and well-known source. Not all oxides are useful to humans, but several varieties play key roles in industry, cosmetics, and art. Manufacturers often rely on them to add pigment as well as to provide certain electronic and magnetic properties to things like bankcards and digital scanning devices.

The pigmentation used in the cave paintings at Lascaux was derived from iron oxide.
The pigmentation used in the cave paintings at Lascaux was derived from iron oxide.

Where it Comes From

Iron is a metallic element with the chemical symbol Fe, and is one of the most prolific and commonly occurring mineral substances on Earth. Scientists estimate that is found in approximately 5% of the planet’s crust, and exists in its core, too. Iron turns to iron oxide when it comes into contact with oxygen, either on its own or in combination with other elements like water. When the mineral is exposed to water and air for extended periods of time it will usually produce rust, which is a reddish-brown oxide.

Iron oxide rust on the surface of a chain.
Iron oxide rust on the surface of a chain.

Deposits of iron oxide occur in the soil, too. Experts usually believe that these were created by the precipitation of iron from seawater during the Proterozoic Eon some 1.6 billion years ago. These deposits are found in locations around the world, though the greatest concentrations tend to be in what is now the United States, India, Australia, China, Brazil, and Russia.

Black iron oxide pigment is often used in mascara and other cosmetics.
Black iron oxide pigment is often used in mascara and other cosmetics.

Different Types

Iron oxidizes a couple of different ways, and the results fall across a spectrum with some being mostly iron and others mostly oxygen. The ending color and technical specifications vary accordingly. There are two primary forms, known as (II) and (III), of the oxide in nature, though different elements and compounds sometimes draw from both sources. Rust, for example, is known as iron (II, III) oxide and has the chemical structure Fe2O3, though the (II, III) designation is also given to magnetite, a compound with the structure Fe3O4; a number of other compounds can also be included in this grouping. In most cases numerical designations say more about how the elemental iron and oxygen bind together than what the substance looks like.

Iron oxide can be found in eye shadow.
Iron oxide can be found in eye shadow.

Color matters, too. In most cases iron with heavy (II) concentrations tends to towards deep black and charcoal in color, while those with a (III) composition fall more on the reddish brown end of the spectrum. The planet Mars, for example, is often known as the “red planet” thanks to the high concentrations of iron (III) oxide on its crust and in its soil.

Iron oxide can be found in facial cream.
Iron oxide can be found in facial cream.

Use in Electronics

Among stable, room temperature elements, there are usually only three that are naturally magnetic, namely cobalt, nickel, and iron; among these, iron is usually the most magnetic, which manufacturers often capitalize on in the production of magnets, electronic parts, audio and video cassette tapes, and bank and magnetized credit cards. In these cases a bit of powdered oxide is combined with other elements and sealants to create magnetic tapes or bands that can be used to help keep working parts charged and in place. That the oxide occurs naturally in nature helps keep costs down, too.

Some sunblocks are manufactured using iron oxide.
Some sunblocks are manufactured using iron oxide.

Cosmetic Applications

The cosmetics industry uses the compound to create various pigments in make-up as well. Most oxide forms are non-toxic, water repellent, and do not run or bleed, making them an ideal additive to products like mascara, liquid and powder foundation, and eye shadow. Oxides can also be found in certain types of health products such as talcum powder, facial cream, and body cream. Some sunblock products contain it as well. Its structure is often thought to help block the sun’s harmful ultraviolet rays from damaging human skin.

Importance in Art

In the art world, iron oxide is used to create pigments such as burnt sienna and burnt umber. Colors and paints made this way tend to be permanent and long lasting. Though the precise method of coloring paints has changed somewhat over time, the basic concept has been at play since the prehistoric age; the cave paintings at Lascaux, France, are just one example of how long this compound has been used and how well paints made with iron last. Modern manufacturers rarely rely on it alone to form base colors and pigment foundations, though it is often still an important ingredient.

In Industry

The compound in its various types and combinations has a range of different uses in industry. Pigments are frequently used to dye such things as commercial-grade paint, concrete, leather, and shoe polish, for example; products like tiles and rubber sometimes also contain it for color and stability. Iron oxide is also added to different nutrients, feeds, and medications in trace amounts, usually as a way of maintaining chemical balance between different active ingredients.

Iron oxide may be found in shoe polish.
Iron oxide may be found in shoe polish.

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Discussion Comments


Over the course of several years, I became increasingly allergic to cosmetics. Aside from hives, my eyebrows and eyelashes fell out and I temporarily lost part of my vision in one eye. I used the Safe Cosmetics website to search for various formulations, with poor results. I ultimately found a site that uses only one ingredient: iron oxide. My reaction was quick and severe.


Wow. Often times we put on makeup such as eyeliner and never stop to think what it's made of. I'm going to use black iron oxide in my soaps just because it looks cool, but wanted to know if it's really safe to use? Oxygen and iron. Well, our body needs both right?


is e172 OK to give to dogs or are there any side effects?


I didn't know that hematite and iron oxide were the same thing. I suppose they are referred to as each in very different situations, so someone like me who doesn't know much about the scientific things relating to metals and elements probably would not know.


While I knew that iron oxide was in a lot of products, I did not realize it was this many, or that there were multiple kinds used. How fascinating that one iron oxide pigment is black, while another is red. I wish I understood the chemistry enough to know why that is.

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