[Michael Cule]

I don't see any objection to a wizard who has seen aluminium and can use magic to analyse it being able to find sources of the ores it is extracted from.

It would require magical research to create a magical means of extracting the stuff. IIRC (quick Wikipedia check, yep) the means of extracting is used on Earth requires quite sophisticated chemistry and a shedload of electrical power which might be difficult to simulate with the magical means of producing lightning known on Yrth and would certainly attract the attention of the Ministry of Serendipity or its local equivalent.

But magical research to create an 'extract aluminium' spell isn't impossible. I'm not sure it would be worth the expense, effort and possible unpleasant attention from the Ministry though. Would the lighter aluminium based chainmail be worthwhile? I'm far from convinced that a lighter metal is what you want for melee weapons, baseball bats or not.