Is iron ore flammable? (A Review)

This article will answer the following question: “Is iron ore flammable?”. We will show which are iron ores, what they are made of, and how flammable they can be.

Is Iron Ore Flammable?

No. Iron ores are inorganic compounds mainly made of iron oxides. They present no flammability and are not considered combustible. Iron oxides are byproducts of iron combustion that can’t burn again.

What is iron ore?

Iron ores are rocks and minerals that are composed of metallic iron.

The ores are found naturally. Iron is extracted from them for commercial purposes. The most common are: magnetite, hematite, goethite, limonite, and siderite.

The compounds can be simple oxides, hydrates, hydroxides, carbonates, and sulfides. Iron is mainly in the form of iron(II) or iron(III). 

Pure forms of iron can’t be found in Earth’s crust but can occur naturally by meteor falls.

What is iron?

Iron is a solid metal that can be found naturally in the form of ores or crafted into many kinds of alloys. Pure iron is normally obtained through chemical reactions.

Pure iron can’t melt until reaches at least 1500ºC/ 2738ºF.

Iron is hard, friable, and fusible. It is used to produce other alloys, mostly steel. Forged iron contains only a few percent of carbon, but it enhances its durability, fracture resistance, and strength.

Iron has the ability to form many kinds of ores. Its chemistry is wide.

Steel is an alloy made with the addition of other minor compounds like manganese, nickel, sulfur, titanium, phosphorous, tungsten, cobalt, and niobium.

Stainless still is typically made with an additional 11% chromium, making the material oxidation-resistant.

Iron is known since prehistoric times, at least 5 thousand years ago. It is the cheaper and most abundant of all metals available on our planet.

Iron chemistry

Iron is a chemical element, an atom. All atoms humanity has found or created are expressed in the periodic table. 

The periodic table is just a convenient way humans found to write about atoms. Every atom there has a neutral charge, meaning that they have no excess or lack of electrons.

In the picture above you can see an atom of iron and its place in the periodic table. The way an atom is written there is not exactly the best, more common, or stable. It’s just a representation.

But iron can be found in a pure form, similar to what’s in the table, bonded with other twin irons. These are the forms that can burn, they react with air’s oxygen to produce iron oxides and often, ores.

All those green balls are the 26 electrons that iron has. These are the particles that participate in chemical reactions. An atom nucleus is never touched unless there’s a nuclear fusion or fission happens.

When for some reason an iron loses two or three electrons, it becomes a cation named Iron(II) or Iron(III) [Fe+2 or Fe+3]. 

This can happen in an aqueous solution (the cations become a free species), or they can form molecules.

What are ores?

Ores are found naturally in rocks and soils.

They are formed by the conjunction of specific environmental conditions, various processes, and sources, and are often bound to the geography of a place. 

Sometimes they come from the ground, formed mainly by lava, sometimes they are deposits of something else on the surface or both. But their genesis is always a complex result of many things.

But just like a cake, rocks can look very different from one another, even if the same ingredients are used.

Ores are typically made from rocks and sediments, containing important compounds that can be mined, extracted, and altered for commercial purposes.

What are iron ores?

Around 60% of all iron ores on our planet are in the form of sedimentary rocks, made of iron oxide layers interleaved with quartz (SiO2).

In the picture above we present black-banded ironstone. It was formed more than 2 billion years ago, by the deposit of iron compounds at the bottom of a sea.

What happens is that weathering and erosion slowly broke down other rocks, especially originating from magma. The seawater then carried these geological detritus to the bottom, which accumulated.

After the accumulation, the sediments suffered a process called cementation. The water eventually dried out, and what was left were strongly cohesive layers of inorganic material.

Each rock in each region of the world has a different formation process and is intimately related to the oxygen in the atmosphere.

If the rock sources are formed when there was not much oxygen on the surface, for example, the rock will have less oxygen as well.

Like many other inorganic compounds, iron ores present themselves in the form of a crystal.

Crystals are small units of a certain kind strongly attached to each other, in ionic bondings, that create a macrostructure.

Can iron itself catch fire?

Yes. Pure iron can burn if it is in a physical form that makes it possible (finely divided or small particles, not as bars).

Have you ever wondered why a stove’s fire is blue, while a fire pit is something between red and yellow?

The fuel is in the form of gas. The particles are much simpler and smaller than wood, for example. The gas is burned all the way to the form of carbon dioxide and water.

The combustion of hydrocarbon gases such as butane occurs much more readily, and evenly. It doesn’t produce many byproducts because the combustion is more or less complete.

Incomplete combustions happen when the fuel, oxygen, and heat ingredients are not in an ideal form. Fumes, carbon monoxide, and smoke are examples of byproducts from an incomplete reaction.

Flames themselves are also part of incomplete combustion. There are countless intermediate products in any kind of flame. The different colors in a fire are the result of different stages of burning.

But when pure (and let’s say, powdered or wool) iron burns, there aren’t any other relevant byproducts, only iron oxides. The burning is much cleaner because of that, so no flames appear. 

But one of the results of the combustion is irradiating heat, which warms up the unburned pieces of iron and the iron oxides, making them incandescent. 

The light you see when someone plays with a burning piece of iron wool is due to this incandescent effect. The warmth itself is not visible, but the things that it heats up are.

Which are the iron ores? Are they flammable?

As we saw, iron is the element that can burn. When it oxidizes slowly in the air (corrode) or when it burns quickly (combustion), it generates iron oxides.

Iron oxides are therefore the byproducts of iron combustion. When something burns, oxygen atoms “get in” the molecule (they literally travel close to the fuel molecules and create chemical bondings).

Therefore, an oxide is the result of oxidation, which is nothing but a reaction with oxygen. Because the new molecule is stable, the oxygen “chooses” to stay bonded. We can write it like this:

4 Fe + 3 O2 2 Fe2O3 + heat

Iron combustion only happens when a reaction like this happens. Therefore, if the iron ore contains maily iron oxides, it shouldn’t present no flammability.

Magnetite

Magnetite has the chemical Fe2+Fe3+2O4, it’s made of iron(II) and iron(III). It can present many shapes and different compounds depending on the source, but it’s mainly made of those oxides.

It can occur in banded iron formations, magnetofossils, metamorphic and igneous rocks.

Magnetite is mainly made of iron oxides, it cannot burn even in a powder form.

Hematite

Hematite, or haematite, is one of the most common iron oxides. It has the chemical formula Fe2O3 and, like other ores, is an inorganic oxide compound that cannot burn.

Goethite

The mineral is made of iron(III) oxide-hydroxide, which has the formula  FeO(OH), or as hydrate forms (FeO(OH)·nH2O, where “n” is a number). 

Besides the iron oxide, contains 25% crystalline silica, 6% aluminum oxide, and 2.3% manganese compounds. None of these are flammable.

Limonite

Limonite also contains iron(III) oxide-hydroxides. The mineral doesn’t present any other relevant mixtures, so it’s not flammable.

Pyrite

Also known as “fool’s gold” due to its visual resemblance to gold, Pyrite is the only iron ore that presents flammability. The material is made of FeS2, a molecule that can decompose itself in a fire and liberate metallic iron.

When pyrite decomposes it doesn’t really liberate any heat. The chemical reaction would occur like this, overall:

FeS2(solid) → Fe(solid) + 2S(gas) + “cold”

In chemistry, we say that this reaction is endothermic. Combustions, although, are exothermic, and it’s the very only reason why we burn fuels and get energy from them.

But if tossed into a fire or under heating (and in the presence of oxygen), pyrite will naturally decompose itself, and the iron resulting from it will burn, unleashing a good amount of energy.

 4Fe(solid) + 3O2(gas) → 2 Fe2O3(solid) + Heat

Therefore, pyrite is considered a flammable solid.

Conclusion

Iron ores made of inorganic iron oxides cannot burn. Iron oxides are already the product of the combustion reaction (oxidation, actually), and cannot burn again because no more oxygen can get in there. 

But other ores like pyrite, which contains FeS2, sulfur instead of oxygen, can burn. It is a fire hazard and was used as a source of ignition in the past.

Frequently Asked Questions (FAQS): Is Iron Ore Flammable?

Is iron ore renewable or nonrenewable?

Iron is a non-renewable material. Iron ore is a natural resource, its quantity is limited on our planet. It takes billions of years to be formed, thus it’s a non-renewable resource.

Although there’s a lot of iron in Earth’s crust, it’s really abundant. So it won’t end anytime soon. The biggest problem is that mining does really big harm to the environment.

Is iron ore a mineral?

Iron ores are minerals, there are many types of them. They can be mined in Earth’s crust by humans, in the presence of strong reductant compounds, to craft pure iron. Most iron ores are oxides.

Is iron ore magnetic?

Many kinds of iron ores are magnetic, especially the ones that contain different atoms or ions such as Fe2+ and Fe3+, it’s what happens in magnetite ores.

Citations

https://pubchem.ncbi.nlm.nih.gov/compound/91502
https://en.wikipedia.org/wiki/Iron_ore
https://en.wikipedia.org/wiki/Ore
https://en.wikipedia.org/wiki/Ore_genesis#Iron
https://en.wikipedia.org/wiki/Banded_iron_formation
https://en.wikipedia.org/wiki/Sedimentary_rock
https://en.wikipedia.org/wiki/Pyrite

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