Iron
Where did iron come from?
Iron atoms were born in dying stars; most iron ore on Earth's surface formed when oxygen made by living things rusted the iron dissolved in the sea.
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In three stops
Where were its atoms born?
Iron forms in the cores of massive stars and in the explosions of stellar remnants called white dwarfs. It is the last stop where a star can make energy by fusion: making anything heavier than iron costs energy instead of releasing it. A massive star whose core fills with iron collapses and explodes as a supernova, scattering the iron into space.
How did it form on Earth?
About a third of Earth's mass is iron, mostly in the core. The rich iron deposits near the surface mainly formed 2.5–1.8 billion years ago: oxygen made by living things rusted the iron dissolved in the sea and it settled on the bottom. These layered “banded iron formations” are the main source of iron ore today.
What did humans make of it?
The first iron people used fell from the sky: beads about 5,000 years old found in Egypt were made of meteoritic iron. Smelting iron from ore came later, and Anatolia is one of the earliest known centres of ironworking. Today iron ore is heated with coke in blast furnaces; the oxygen is removed and iron is left behind.
Did you know?
Your blood holds about 3–4 grams of iron too: enough for a small nail. It sits at the heart of haemoglobin, the molecule that makes blood red and carries oxygen.
Tree →See it in the journey: Stars die and scatter elements (Over billions of years, again and again) →See it in the journey: Earth forms (4.54 billion years ago) →See it in the journey: The Iron Age (Around 1200 BCE) →