The thing about Rock crystal, Bauxite, and pretty much everything else that's missing is this: as Toady stated, the worldgen has a large preference for metal-bearing minerals (due to some user feedback), and thus tends to overrule the spawn rates set in the raws when allocating the minerals. To the point where ANY metal ore will COMPLETELY overwrite any non-metal-bearing mineral in any given stone layer. So, magnetite will overwrite any bauxite and any other non-ore mineral set to spawn as clusters. It's the reason why it's so widespread - while technically it shouldn't be. This is a bug, and a large one at that, but until Toady thinks up a way to remove it without completely removing the relevant minerals (for magnetite, shouldn't removing its METAL tag and just adding it to reactions make a temporary fix?), we're stuck using mods - like mine. I'll see what can be done about magnetite, and add it to my mod, so that people don't have to go too far to look for it.
Edit: Hm, read about the magnetite on the wiki. Yeah, it seems pretty widespread. And placed correctly. BUT!!! It also seems to be present in SAND, of all things! So, if I succeed in nerfing magnetite that way, maybe I could rebuff it by adding small occurences of it into sand? I'll see if the raws are flexible enough to allow clusters of soil within soil...
[ December 11, 2007: Message edited by: Sean Mirrsen ]
Well, guess not. Magnetite remains over-intrusive even if its iron-producing capabilities are only mentioned in reactions.
I'll try an earlier version though, maybe reveal can *reveal* some insights...
[ December 11, 2007: Message edited by: Sean Mirrsen ]