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What is Iron Oxide?

Desi C.
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.

Where it Comes From

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.

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.

Different Types

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

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.

Use in Electronics

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

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.

Cosmetic Applications

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

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

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

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.

Frequently Asked Questions

What is iron oxide and where is it commonly found?

Iron oxide is a chemical compound made up of iron and oxygen, typically recognized by its rusty, red appearance. It's commonly found in soil, rocks, and minerals on Earth's surface. Iron oxide is also abundant on Mars, giving the planet its characteristic red color. It's a key ingredient in pigments and is used in various industrial applications.

How is iron oxide formed?

Iron oxide forms through the oxidation process, where iron reacts with oxygen, often in the presence of water or moisture in the air. This reaction can occur naturally over time, leading to the rusting of iron metal or the reddening of rocks. It can also be synthesized industrially for use in paints, coatings, and other products.

Are there different types of iron oxide, and if so, what are they?

Yes, there are several types of iron oxide, each with unique properties and uses. The most common are hematite (Fe2O3), magnetite (Fe3O4), and goethite (FeO(OH)). Hematite is used as an iron ore, pigment, and in polishing compounds. Magnetite is valued for its magnetic properties and is also an iron ore. Goethite is used as a pigment and an iron ore as well.

What are the industrial uses of iron oxide?

Iron oxide has a wide range of industrial uses. It's a key component in pigments for paints, coatings, and cosmetics due to its color and stability. In construction, it's used to color concrete and ceramics. Iron oxide is also utilized in the steel industry as a raw material for iron production and in magnetic storage media for its magnetic properties.

Can iron oxide be harmful to humans or the environment?

Iron oxide is generally considered non-toxic and environmentally benign. However, inhaling iron oxide dust can cause respiratory issues, so workplace exposure is regulated. In the environment, iron oxides can influence soil and water chemistry, but they are also crucial for nutrient cycling and are not inherently harmful to ecosystems.

Is iron oxide important for any biological processes?

Iron oxide plays a vital role in biological processes. Iron is essential for oxygen transport in the blood, as part of hemoglobin, and is crucial for many enzymes' functions. While not directly used biologically, iron oxides in soil can affect the availability of iron for nutritional uptake by plants and microorganisms, influencing ecosystem health and productivity.

Discussion Comments

anon321590

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.

anon292224

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?

anon217882

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

hyrax53

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.

panda2006

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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    • The pigmentation used in the cave paintings at Lascaux was derived from iron oxide.
      By: Bayes Ahmed
      The pigmentation used in the cave paintings at Lascaux was derived from iron oxide.
    • Iron oxide rust on the surface of a chain.
      By: Yali Shi
      Iron oxide rust on the surface of a chain.
    • Black iron oxide pigment is often used in mascara and other cosmetics.
      By: haveseen
      Black iron oxide pigment is often used in mascara and other cosmetics.
    • Iron oxide can be found in eye shadow.
      By: ctvvelve
      Iron oxide can be found in eye shadow.
    • Iron oxide can be found in facial cream.
      By: Konstantin Yuganov
      Iron oxide can be found in facial cream.
    • Some sunblocks are manufactured using iron oxide.
      By: Nobilior
      Some sunblocks are manufactured using iron oxide.
    • Iron oxide may be found in shoe polish.
      By: Margrit Hirsch
      Iron oxide may be found in shoe polish.