60 Fun Facts About Iron

What is the chemical symbol for iron?

It comes from the Latin word ferrum.

What is the atomic number of iron?

It sits in group 8 of the periodic table, in the first transition series.

By mass, iron is the most common element where?

On Earth as a whole. Most of the planet's iron is locked away in the core, which is largely made of it, so at the surface it is far scarcer: only about 5% of the crust.

Which element is the only metal more abundant than iron in the Earth's crust?

Aluminium. It bonds so tightly with oxygen that it is locked into the crust's rocks and almost never turns up as native metal, which is why nobody isolated it until the 19th century.

Which metal is used to coat iron and steel in galvanising, shielding them from corrosion?

Zinc. It protects twice over: the coating seals the surface, and where it is scratched the zinc corrodes first, sacrificing itself so that the iron underneath is spared.

Why does rusting keep eating into iron instead of stopping at the surface?

Rust swells and flakes off, baring fresh metal to air and water. Many other metals tarnish too, but their oxide clings on as a tight skin, so the damage stops there.

Iron loses its magnetism above a temperature named after which physicist?

Pierre Curie showed in 1895 that heat wipes out a magnet's pull above a critical temperature, about 770 °C for iron. He married Marie Skłodowska that same year, and their work on radioactivity followed.

Earth's inner core is hotter than iron's melting point, so what keeps it solid?

Pressure of more than three million atmospheres holds the inner core solid, though it is about as hot as the Sun's surface. As the planet slowly cools, the ball grows as molten metal freezes onto it.

Which naturally magnetised iron mineral provided the earliest compasses?

Lodestone means 'way stone'. Left free to turn, it swings to line up north and south, and an iron needle stroked with it does the same.

Iron oxide dust gives which planet its famous colour?

Mars is coated in iron minerals that have oxidised, the same chemistry that reddens an old nail. The Romans thought the colour looked like blood and named the planet after their god of war.

Iron's abundance on rocky planets is due to its production during which cosmic events?

Type Ia supernovae are white dwarf stars blown apart by runaway fusion. The blast forges radioactive atoms that decay into iron over the following months, and flings them out to end up in new stars and planets.

What is believed to generate Earth's magnetic field?

Electric currents in the liquid iron outer core, kept churning by escaping heat, work like a dynamo. The field they create fends off the solar wind, which would otherwise strip away the upper atmosphere.

Much of the body's spare iron is stored in which organ?

The liver banks spare iron and releases it when supplies run short, which is why animal liver is such an iron-rich food. It is also why the organ suffers when the body takes in too much.

Which iron-containing protein carries oxygen in red blood cells and gives them their colour?

Hemoglobin holds four iron atoms, each able to grip one oxygen molecule. Loaded with oxygen it is bright red, and once it has handed its cargo over it turns a darker, purplish shade.

Which protein carries absorbed iron through the blood to cells?

Transferrin picks up iron salvaged from worn-out red blood cells as well as iron from food, then ferries it to the bone marrow, where it is built into new cells.

Why is carbon monoxide poisonous?

It takes oxygen's place in the blood, clinging to the iron in red cells far more tightly than oxygen can, so the body's tissues starve. With no smell or colour, the gas gives no warning.

A lack of iron is the most common nutritional cause of which blood condition?

Anemia means having too few healthy red blood cells to carry oxygen, which leaves people tired and short of breath. Young children and women who menstruate or are pregnant are affected most.

Iron deficiency can trigger pagophagia, a compulsive craving to chew which substance?

Ice. A compulsive ice-chewing habit is a recognised sign of low iron, and the craving often eases once supplements bring the level back up.

What is the medical name for the genetic iron-overload disorder?

Hemochromatosis makes the gut take in more iron than the body can use, and the excess builds up in the organs until it damages them. The usual treatment is simply to draw off about a pint of blood on a regular schedule.

Which metal is alloyed with iron to make stainless steel resist corrosion?

Chromium forms an invisible oxide skin on the steel that shields the iron beneath. Sheffield's Harry Brearley, often credited with the discovery in 1913, was really after a gun barrel that wouldn't wear out.

Sea mussels use iron-based bonds in their cuticles to do what?

Grip rocks in the ocean: the threads that anchor a mussel wear a thin coat cross-linked with iron, hard enough to resist grinding surf yet stretchy enough not to crack.

Iron beads buried in Egypt over 5,000 years ago are known to be meteorite metal because they are rich in what?

Nickel is the giveaway: iron that falls from space is rich in it, while iron won from ore holds only traces. Egyptians prized the sky metal for precious objects long before anyone smelted iron.

A dagger forged from a fallen meteorite was found in whose tomb?

Tutankhamun's dagger turned up in 1925 inside the wrappings of his mummy. Egypt was barely smelting iron in his day, so a blade of the sky-fallen metal was a rarity fit for a king, and it got a hilt of gold.

Which Bronze Age people were long credited with being the first to smelt iron from its ores?

The Hittites were long said to have guarded the secret of iron and built an empire on it. Yet smelted iron turns up centuries before that empire arose around 1600 BC, so the craft is older than they are.

Which rock is fed into a blast furnace with iron ore to carry off its impurities as slag?

Limestone burns to lime in the heat, grabs the sandy impurities in the ore and floats them off as molten slag. The slag isn't wasted either: it ends up in concrete and road beds.

The Iron Age began when iron tools displaced alloys of which metal?

Copper, hardened with a little tin, makes bronze, the costly metal of earlier elites. Iron was far cheaper, so for the first time whole peasant armies could carry metal weapons.

In which country was cast iron first produced?

China was pouring molten iron into moulds well over 2,000 years ago, turning out farm tools and weapons in bulk. Europe caught up only in the late Middle Ages, when it began casting cannon.

Cast iron is brittle where steel is tough because it holds far more of which element?

Carbon makes up more than 2 percent of cast iron, against less than that in steel. The extra lets it melt easily and pour into moulds, but a hard knock cracks it instead of bending it.

Which landmark was built from puddled wrought iron rather than steel?

The Eiffel Tower is about 7,300 tonnes of wrought iron held together by 2.5 million rivets. To keep it from corroding, the whole structure is repainted roughly every seven years.

In 1709 Abraham Darby began smelting iron with which fuel instead of charcoal?

Coke, baked from local coal, was cheap and strong enough to carry far heavier furnace loads than crumbly charcoal. Darby used his iron for thin-walled pots that could compete with brass ones.

Which US Navy frigate is said to have earned the nickname 'Old Ironsides' when British shot bounced off its oak hull?

USS Constitution battered HMS Guerriere into surrender in that 1812 duel. Launched in 1797, she is still a commissioned Navy ship, crewed by serving sailors in Boston.

Builders of the world's first major cast-iron bridge borrowed their joints from which trade?

Carpentry: the Iron Bridge over the Severn, opened in 1781, is locked together with dovetails and other woodworking joints. It proved strong enough to survive the river's great flood of 1795.

Which inventor's 1850s process blew air through molten pig iron to make cheap mild steel?

Henry Bessemer found that the blast of cold air did not chill the metal: burning out the impurities made it hotter still. He announced the process in 1856 as making steel 'without fuel'.

Iron is the catalyst in the Haber process, which turns nitrogen from the air into which fertiliser ingredient?

Ammonia made over hot iron is the starting point for almost all synthetic nitrogen fertiliser. By one estimate, the crops it feeds support about half the people on Earth.

Which chemist passed steam through a red-hot iron tube to show that water is a compound?

Antoine Lavoisier's hot iron seized the oxygen from the steam and let hydrogen flow out of the far end. Water, counted as an element for 2,000 years, had been split in two.

The Iron Cross medal was first awarded in 1813, in a war of liberation against which ruler?

Napoleon's grip on central Europe drove King Frederick William III to found the medal for the war to throw him out. It was revived for three later wars, the last time by Hitler on the day he invaded Poland.

Sprinkling iron dust on iron-poor stretches of ocean sets off huge blooms of what?

Algae in those waters have every nutrient they need except iron. John Martin, the oceanographer behind the idea, joked: 'Give me a half tanker of iron, and I will give you an ice age.'

Which two iron oxide minerals are the major ores of iron?

Hematite and magnetite are both iron oxides. Hematite takes its name from the Greek for blood, after its red colour, and ground to powder it is used as a red paint pigment.

As of 2025, which two countries dominate the world's seaborne iron ore trade?

Australia and Brazil together ship most of the ore sold abroad. Almost all iron ore, about 98 percent, has a single destiny: the furnaces that turn it into steel.

Banded iron formations, mined as taconite in North America, nearly all formed in which span of Earth's history?

Precambrian seas held iron in solution. One theory is that the first oxygen-making microbes turned it into oxides that sank in layers, so the bands may record the planet's air becoming breathable.

Pyrite, a mineral of iron and sulfur, is better known by which nickname?

Fool's gold glitters like the real thing. Its proper name comes from the Greek for fire, and it does throw sparks when struck: early wheel-lock guns used a chip of it to light the powder.

The Inuit of which land made tools from an iron meteorite that Robert Peary later shipped to New York?

Greenland's Inuit worked pieces of the metal into knife blades and harpoon tips for centuries. In the 1890s the explorer Robert Peary hauled the largest chunk, 34 tons, off to a New York museum, where it is still on show.

Who told an audience in Fulton, Missouri, in 1946 that an 'iron curtain' had descended across Europe?

Winston Churchill was out of office when he gave the speech, and the phrase was not his invention: it had been a metaphor since the 19th century. His use made it the name for the Cold War's dividing line.

What has protected Delhi's 1,600-year-old iron pillar from corroding away?

A phosphate film on its surface is the secret. The old smiths' iron was unusually rich in phosphorus, and over the centuries it has grown a thin crystalline coat that seals the metal from Delhi's weather.

Which vitamin helps the gut absorb the iron in plant foods?

Vitamin C eaten at the same meal helps the gut take up plant iron, which is otherwise absorbed poorly: compounds such as the phytates in grains and beans hold it back.

Which leafy vegetable is rich in iron that the body absorbs only poorly?

Spinach is rich in iron on paper, but compounds in the leaf hold most of it back. The iron in meat and fish comes in a different form that the gut absorbs far more easily.

A farrier is a smith who specialises in which job?

Shoeing horses takes a smith's hammer and a vet's eye: a farrier trims and balances each hoof before nailing the shoe on. The name goes back to the Latin word for iron.

Which famous pigment is a compound of iron and cyanide?

Prussian blue is what put the blue in blueprints. Light turns iron salts on the sensitised paper into the pigment wherever the drawing's lines don't shade it, leaving white lines on a blue sheet.

The 'iron lung', a metal tank that breathed for its patients, is tied to epidemics of which disease?

Polio could paralyse the breathing muscles, so the tank's bellows pulled air out of the chamber and let it back in, making the chest rise and fall. Once vaccines arrived in the 1950s, the machines fell out of use.

Which Greek poet's Works and Days named ages of man after gold, silver, bronze and iron?

Hesiod set his own time last, in the age of iron, when 'men never rest from labour and sorrow'. He wished he had either died before it began or been born after it ended.

Which language's word for railway is Eisenbahn, literally 'iron track'?

German builds the word from Eisen, iron, and Bahn, a track, the same Bahn as in Autobahn. The name has outlived the metal: the first steam railways ran on iron rails, but modern track is steel.

A cast-iron pan is 'seasoned' by baking on a thin layer of what?

Cooking oil, heated far enough, bonds to the metal as a slick coating much like plastic. That layer is what makes an old skillet non-stick and keeps the bare iron underneath from rusting.

Stepping on a rusty nail is popularly linked with which disease, really caused by bacteria in soil?

Tetanus has nothing to do with rust itself. The bacteria's spores live in soil and dust, and an old nail lying outdoors is simply a dirty object that can carry them deep into a wound.

Blood Falls, a glacier outflow stained red by iron-rich brine, is found on which continent?

Antarctica's Blood Falls seeps from salty water sealed beneath Taylor Glacier for more than a million years. The brine comes out clear and turns red only when its dissolved iron meets the air.

Kiruna, an Arctic town that began moving two miles in the 2010s to escape its own iron mine, lies in which country?

Sweden is shifting Kiruna's centre east as the mine eats the ground under the old one. In August 2025 the town's 672-tonne church made the trip in one piece, rolled along a specially prepared road.

The Mesabi Range, the chief iron ore district of the United States, lies in which state?

Minnesota's Mesabi Range takes its name from an Ojibwe word for giant. When its rich ore ran out in the 1950s, the mines turned to taconite, a hard low-grade rock that is crushed and baked into pellets.

Which planet has an iron core so oversized that it spans about 85 percent of the planet's radius?

Mercury is little more than a ball of metal in a thin rocky shell. That is why the smallest planet is also the second densest, beaten only by Earth.

The famed Damascus sword blades were forged from wootz steel, first made in which country?

India's smiths sealed iron and wood chips in clay pots and fired them until the metal melted into steel. Traders carried the ingots west, where they were forged into the patterned blades named after Damascus.

Which Victorian London landmark was built from prefabricated cast-iron parts, then taken apart and rebuilt across the city?

The Crystal Palace was designed by a gardener, Joseph Paxton, who scaled up his greenhouses to house the Great Exhibition of 1851. It stood in south London until a fire destroyed it in 1936.

Early European smiths gathered much of their iron ore not from mines but from where?

Bogs and marshes grow their own ore: iron seeping in with the groundwater settles out as brown lumps, helped along by bacteria. A bog dug out by one generation can be harvested again by the next.