Saturday, June 21, 2008

Meteors in Forge and History

Do you typically find meteors containing pure iron ore? How pure
typically?

Can a meteor be worked without much further smelting, or does the
metal still need to be pulled out of the rock to work it?

Could you cold hammer meteoric metal into a tool / dagger without
actually heating it in a forge, or would it be practically useless?

Just some questions from an enquiring mind!

Scott


(I had this question forwarded to me, originally posed on the Eldormere discussion group. I don't actually get this discussion group directly (volume interfering with business communications). My wife this been forwarding this topic thread to me however. The original request from Scott was directly about working a found meteor into some kind of object.)

Unlike the other people who made comments, I have actually forged meteor iron myself.

Objects made from meteors are easy to distinguish in the archaeological record, from the per centage content of nickel. Typical meteor nickel contents will range from 7 - 15 %. It was not possible to make 'artificial' alloys with this high a nickel content until the late 1800's. Some of the earliest iron objects in existence (the dagger in King Tutankhamun circa 1300 BC tomb a striking example) are in fact made from this non terrestrial source of metal. Cold worked meteor iron is found in Inuit contexts as well. One surprise in the sample of knives in the collection of the London Museum is that roughly 15 % show some traces of nickel content (hence most likely the inclusion of meteor source materials)
Metallic iron does not naturally occur on the earth's surface - period. There are two exceptions, the significant case being masses of various sizes that are the remains of meteors. The first human smelted iron objects date back to roughly 2500 BC (+ / -), but iron does not become a major material till much closer to the 500 BC time frame. The earliest iron production appears to be centered out of what is modern day Turkey. There is considerable debate currently on just how humans ever figured out how to convert iron oxide ores (essentially rust) into useable metal. The Greeks made only limited use of iron, it was the Celts (about the same time frame) who were about the first culture to be based on iron, especially as weapons. In any case, the creation of a workable iron bloom from iron ore was (and still remains) a challenging and resource intensive effort. Iron was 'expensive' on many levels, and not the wide spread material it has become in the modern era. During the Viking Age, the average 'load per person' was closer to 2 kg each (one axe, one knife, plus your share of the household cookware or boat rivets).

First - the metal in nickel iron meteors will vary considerably in both metal content and more importantly in physical structure. Nickel in an iron alloy serves to toughen the metal, making it more resistant to changing shape. This applies even at the hot forging stage, so considerably more effort is required to hammer form even modern low nickel alloys. (A typical modern stainless steel is likely to have between .5 to maybe 2 per cent nickel.) This means there is a potential problem forging meteor metals using early blacksmithing equipment, using these smaller and lower heat charcoal fires and on extremely small anvils. (The two typical ways to deal with rigid metals is to either increase the forging temperature - or use a bigger hammer.)

The second problem is the physical structure of the meteor itself. A small piece is going to be full of stress cracks after its passage through the atmosphere and the impact with the earth. On the two occasions I have attempted to forge small meteors (roughly half walnut sized) the material almost instantly started to fragment apart. I had no solution to this problem, as the small pieces were too hard to manipulate. If they had been larger, it might have been possible to forge weld the material back into a solid mass. This process might have proved easier in charcoal, despite the lower heat available. The technical reason is that nickel has a serious problem absorbing sulfur - a typical impurity in coal. My solution to the fragmentation of the small pieces was to incorporate them inside a layered steel billet. This is illustrative, as most nickel alloys found in an Early Medieval context are in fact found as part of the layers in pattern welded blades.
If the meteor is large enough, the centre of the mass has no time to overheat during its short passage through the atmosphere (even though the exterior may be burning off and then subjected to huge energies on impact). These larger masses could - and historically were - broken up into chunks small enough to be worked by the smith. I have a slab of a huge (many tons) meteor that impacted in Kenya, eons ago. This piece is roughly 3 / 16 inch thick by 2 x 3 inches, and is clear solid metal. (I had a chance to purchase a 'short sword' sized billet of the same material, and still kick myself for not making the investment.) Such pieces are sold by the gram - and are considered a specialized jewelry material to modern artisans. (That smaller piece cost me about $100.)

So - getting back to Scott's original question:
If you were an Saxon farmer, and you dragged out a head sized mass of iron under your plow (which by elimination would have to be of non terrestrial origin) - you would suddenly be a RICH farmer. Working the metal would be extremely challenging for the local blacksmith, given the nature of the material and the limitations of the equipment of the times. Given the inherent rigidity of the metal (and its curious resistance to rusting) the most likely use of the metal would be for weapons making.

Oh - I should note that the whole 'streaks in the sky to rocks on the ground' connection was actually NOT made until the middle 1800's. The whole concept of a 'sky stone' would have been completely unknown (and unthinkable) to the Medieval mind. This is a fiction created by modern fantasy writers.

1 comment:

nathaniel said...

Just found your site while reading up about meteoric iron.

While in D.C. at the freer we saw a meteoric iron knife from 13th century India where a meteorite was seen to hit, retrieved and made into a knife. So at least in India they got the sky metal connection.

quote from www.asia.si.edu (freer museum)

Early pre-Mughal Sultanate period (ca. 1206-1526) works on view include a manuscript page from a Khamse (quintet) of Amir Khusraw Dihlavi. The wide range of Mughal objects on view includes:

* Two allegorical paintings commissioned by the Emperor Jahangir that represent his desires to best his rival, Shah 'Abbas of Persia, and a third that depicts an imaginary visit of King James I of England to the Mughal court
* A Ganga period shrine of Vishnu with consorts that recreates an Orissan temple tower in miniature form
* Several Mughal luxury objects, including a knife made for the Emperor Jahangir out of meteoric iron and decorated with gold inlay; a dagger with a white jade handle inlaid with gold, rubies and emeralds; and an intricately decorated enamel spice box

 

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