“A magic sword is important,’ said Magrat. ‘You’ve got to have one. We could make him one,’ she added wistfully. ‘Out of thunderbolt iron. I’ve got a spell for that. You take some thunderbolt iron,’ she said uncertainly, ‘and then you make a sword out of it.”
– Terry Pratchett, Wyrd Sisters
It may feel like a bit of a cheat in some ways – another instalment that focusses on iron. In some ways, perhaps it shouldn’t come as a surprise though. Iron has been so important to the development of homo sapiens that it gives us the name of an entire age (generally considered to begin 1200 BC and ending as early as 500 BC or as later as 800 AD depending on where you are in the world and where you take your scholarship), and underpins other significant eras including the Industrial Revolution.
There are all sorts of places that we could take this, but we couldn’t have a serious consideration of materials in literature without including thunderbolt iron. Sometimes it comes in different guises, so for example in the Dark Materials Trilogy, by Philip Pullman, the panserbjørne’s characteristic armour is made from ‘sky iron’. Some people use the term ‘star iron’ in an attempt to be different and perhaps a touch poetical, missing the point (probably) that all iron is star iron.
It is strange and not a little inconsistent that iron is seen as being both prosaic and utilitarian and at the same time mystical and fantastic. Iron has been a work-a-day material for approaching 3,000 years, used for pots and pans, tools, and, of course, weapons. It is probably the weapons, particularly swords, that give rise to most of the more thrilling aspects: they form the core of so many epics, with the legends of King Arthur giving the monarch not one, not two, not three but FOUR separate swords.
Special swords often have interesting origins. Sometimes it’s left ambiguous, or just stated that the alloy contains some rare constituent (see for example the bar of “special” steel recovered from the sorcerer Nakano’s cave in Highlander III). Sometimes a real but completely ridiculous or impossible constituent is stated (although I will admit that a specific example doesn’t come to mind). But thunderbolt or meteoric iron not only exists, but has been used, as it were, in anger.
There are two key features of this kind of metal, both of which make it exceptionally useful in the context of smithing. Firstly, the iron that you find on Earth is invariably bound in various mineral forms (ores), typically oxides, but also sulphides, phosphides and the like. You need to get the iron out of the ore, but it took some time for technology to reach a point where the iron could be extracted by heating it – the kinds of temperatures that you need to achieve are only possible in certain kinds of furnaces. Instead, the ancients used a heat’n’beat method, physically working the impurities out of the iron by heating it up and heating it over and over and over again, until they had something useful. Meteoric iron isn’t like that. It’s what is called ‘native’ or ‘free’ metal. In practice it is usually really an alloy with a significant amount of nickel (sometimes as much as 40 wt%) and sometimes other elements in greater or less quantities. Cobalt, for example (which is named after the Kobald, the sprites that Germanic miners believed were to be found deep underground*) is frequently found in alloys of this kind together with trace amounts of more exotic metals (although still found in the Earth’s crust) such as gallium and germanium (which, incidentally, are often used as ‘fingerprints’: objects created from particular meteorites can often be linked back to the parent using the composition of the alloy.
*And as a note, this is also where garden gnomes get their red hats from: this kind of headwear was worn by the same group of miners and hence was transferred to the kobald, who went through a pre-Disney transmogrification into the kitsch cute-but-grumpy stoneware we know and tolerate today.
So we have iron which is not only present in a form that is much easier to work than whatever else is available, it is an alloy containing some interesting additions which can give rise to microstructures that are not normally available. What we always have to remember with the naming of the ‘Ages’ is that they are there for our convenience. Ancient people didn’t suddenly go, ‘oh, right, it’s the Iron Age now is it? Let’s throw away all this bronze rubbish”. Neither did they wake up one morning knowing exactly what to do. No. Mark Miodownik has a really nice visual in his series “Wonder Stuff” of a bunch of ancients sitting round a camp fire and in the morning they found they’ve got free copper where they’d used copper containing rocks as a base for the fire. Something like that probably did happen, and something like that probably happened with some iron containing rocks – although they didn’t get free iron, because the camp fire wouldn’t get hot enough. But one day, someone found a rock. They may have even linked it to the meteorite that came down in the night – we know that the connection between the sky and these odd rocks was made from time to time – and they probably thought “this looks a bit like that rubbish that we’ve been beating the living daylights out of…but it looks better somehow, I wonder what happens if I do this…” and that’s how people like Tutankhamun get special daggers at what we are pleased to call the Bronze Age, some 200 years before the Iron Age is considered to begin.