Allomantic metals

[Ambitions Avatar]

What is the distinguishing feature (if any) that determines if a metal has an allomantic use or not? Is there a patterns or system that determines which metals/alloys work? Or is it just the will of Brandon and what he likes?

I haven't heard or seen this addressed before although I'm sure it's come up in the past.

Thanks

[Calderis]

Tin used to be silver, and had to be changed because Brandon misunderstood the composition of pewter. It's just what he chose. 

Quote

Brandon Sanderson

One interesting aspect of the book that I haven't mentioned yet comes with the metal of tin. Originally, tin wasn't one of the Allomantic metals—I used silver instead. You see, I originally paired silver and pewter together, thinking that pewter had a significant amount of silver in it. Well, turns out that isn't the case. (Remember, each set of paired metals is a metal and an alloy made from it.)

My false impression on the belief that pewter is a silver/lead alloy goes back to my childhood. I remember when I used to paint lead fantasy figures that I bought at the local hobby store. One of the employees told me that they would be going up in price because the manufacturers wanted the figures to be safer. They were going to cast them out of pewter instead of lead, because pewter is much less toxic. I asked what the difference between pewter and lead was, and the employee told me that pewter is lead PLUS silver, and that's why the figures cost more.

He meant tin, I guess. Either way, that's stayed with me for quite a long time. I soundly resisted changing silver to tin during the first drafts of the book, even when I found out the truth. The problem is, I really liked the name "Silvereye" for those who burn silver/tin. It sounds far slicker than "Tineye."

I eventually came around, however. Consistency in the magic system is more important than a single cool-sounding name. I blame Hobby Town in Lincoln Nebraska for my pains.

source

 

[Weltall]

There's no in-universe explanation for why some metals work in the Metallic Arts and others do not. The out of universe reasoning for the ones that were chosen is that Brandon wanted some powers to be 'hidden' which meant that they had to make use of metals that wouldn't be in common use during the earliest parts of the timeline. He mentioned elsewhere that he considered repurposing silver for what aluminum does but the former was simply too common so it wasn't reasonable for it to be a 'secret' metal in the way that it needed to be. Similarly the Temporal and Enhancement metals revealed in Era 2 are all things that you're not going to discover by accident.

[Quantus]

So far it's just the will of Brandon, though I have a theory that those 16 specific metals will prove to have been significant in the Shattering of Adonalsium somehow.  At least, that holds true for the 16 base allomantic metals.  Godmetals are a whole other can of worms, sitting over a pit-trap rabbit-hole with a sign marked "Trell This Way" that looks like it was painted by a coyote. 

[Iridium Savant]

The 'key' for figuring out if a metal will cause an allomantic effect is the atomic structure of the metal.  The atoms form a latticework of connections that create specific geometric shapes and patterns.  It is those specific shapes and patterns that determine the effect of the metal I believe.  That is why an impure metal will cause a weak effect, part of the metal you burn has the proper lattice work of geometric shape and part of it doesn't.  The part that is correct burns and channels in the investiture from the spiritual realm (In a weakened way because the geometric shape is rough around the edges) and the impure part gives you metal poisoning partly I believe by breaking its atomic bonds with the burned up metal and trying to chemically stabilize itself with whatever other matter it can find I suspect.  Disclaimer: I am no chemist or metallurgist, this is just what I have gathered from various words of Brandon, some of which I have linked below.

https://wob.coppermind.net/events/337-idaho-falls-signing/#e10133

https://wob.coppermind.net/events/295-west-jordan-signing/#e10097

https://wob.coppermind.net/events/100-rbooks-ama-2015/#e3405