If it were rolled copper and hollow, I would suggest it's a Conical Kaskaskia Native point. It doesn't seem to be rolled or hollow, so I would guess an awl or generic piece.
I wouldn't have agreed with aluminum--only because every piece--and I mean every piece--I've dug has been in nearly the same condition as when dropped. Extremely old pieces have had some oxide damage, but nothing like these pics.
So I'm thinking it may have to do more with the soil.