Raw mineral of a legend – Goethite

What does it look like?

The crystal structure of goethite. The gold atoms are iron, red oxygen and pink are hydrogen. Image generated by the VESTA (Visualisation for Electronic and STructural Analysis) software http://jp-minerals.org/vesta/en/

What is it?

This is the crystal structure of goethite, a material made up of iron, oxygen and hydrogen, FeOOH. It's the main mineral component of rust, and can be often found in the soil. It's also the main iron ore mineral found in limonite, or bog-iron – which was the starting material for most medieval steels. Before modern metallurgists developed blast furnaces to create the quality of steel we used today, the blacksmiths who forged the legendary swords had to often resort to stranger techniques to turn goethite into steel.

Such as the tale of the legendary craftsman, Wayland the Smith, who turns up in a number of medieval sagas and poems from Anglo Saxon literature. Thidrik's Saga tells of how he first produced the sword Mimming, but was unhappy with how it turned out. So he filed down the sword to dust, baked the dust into cakes and fed some starving poultry. He then collected the droppings from these birds, and distilled out the iron from this to forge a new sword. Then, not being happy with the results again – he repeated the whole feeding-birds-a-sword process again!

Apparently in 1955, this process was repeated by some French scientists (who fed the dust-sword to ducks rather than chickens). They also found a number of scientific reasons as to why this process may have improved the steel. One was that the biochemistry of the ducks' digestive processes removed phosphorus – a common impurity found in bog iron.

Where did the structure come from?

The arrangement of iron and oxygen in the structure has been known since 1935, but locating the hydrogen atom in the structure took a little longer. The structure we've featured comes from the first single-crystal X-ray refinement of goethite, published in 2006, #2211652 in the Crystallography Open Database.

Tags: iron   mineral   legend