There was some discussion on another thread about these two metals which reminded me of them, and how they aren't very faithfully represented in DF.
First off, the only "Native Aluminum" I was able to find that wasn't grown in a lab came in tiny little flakes near mud volcanoes, hardly enough to smelt. Besides, it would most likely be mistaken for tin by a culture that did not already know of the metal. And IRL, it wasn't discovered until the 1800's.
Second, Native Platinum contains other platinum-group metals in it that makes it too brittle to work with; the only way to use it was to alloy it with gold. Also, I see nothing about it that would make it more valuable to a preindustrial society like our dwarves have than bismuth. This can be supported by the fact that while the natives of Central America knew about the metal, they didn't use it as much as gold (information limited on the subject, mainly from Wikipedia).
So, my suggestion is this:
- Remove aluminum entirely.
- Make native platinum (renamed 'Platina') only smeltable by alloying with gold (to make white gold), or remove it entirely.
- Make 'white gold' less valuable than gold (roughly equal to electrum), and native platinum the same as native silver or less.
Of course, this would be a pittance to mod; but I'd like to see it in the official version.