And I'm a bit doubtful as to the ability to locate aluminum at all (aside from bauxite, of course).
It's only the third most abundant element in the Earth's Crust, after Oxygen and Silicon. Should be real difficult to find. Pure Aluminum is rare, but Aluminum Oxides are so abundant as to be the basis of most of the mineral's known to man.
Seriously look it up.
Yeah, they're called "rocks" and "soil". Clay, for example, is heavily composed of aluminum, and aluminum is in the majority of all the stones in the game. However, they aren't in any form even
remotely extractable to be used as an actual metal.
It's a little like saying that nitrates are readily available everywhere because N
2 Nitrogen makes up 78% of the atmosphere... it's just in a triple bonded form that renders it almost completely chemically inert and useless except through extremely complex Haber-Bosch processes or nitrogen fixating bacteria.
More seriously, I would like to see it possible, but extremely, extremely expensive to refine aluminum out of bauxite through the use of some very specially made kilns with mechanically powered fans that take up 20 units of charcoal to refine a single unit of aluminum in order to simulate the sort of Napoleon aluminum forks type of ultra-expensive aluminum, just because
then it would justify being a really rare and valuable metal. The native aluminum can just disappear.
Other than that, I like the platina ideas Arkenstone has been talking about, especially since those sort of history-lesson-as-minor-game-detail thing are what I positively
love about DF.
It's the fact that DF quietly and unassumingly puts real-life sciences into the game for you to learn about without really making a big deal out of it that make the game so much more wonderful to learn about than just arbitrary fantasy world game mechanics. That stands head-and-shoulders over "I don't like realism in fantasy" as a reason to put platina and platinum-gold alloys in DF.