The mineral makeup will not be changed in 33f, because Toady fixed what I was trying to override, and in prior versions it will have an effect only on any new generated world.
So, to only have the "selectable stone" effect, just stick the mineral fusion reaction I posted later into your reactions_standart, and you should have the stones selectable. If you've upgraded to 33f, even generating a new world will not have any effect on mineral placement.
See also: my thread in the modding forum.
As to how it works.
Basically, it labels all the stone in the game as economic. You can see a list of economic stone in the overall information menu ("z" menu), in the Stone section. The game will enable the first basic stone you encounter as available, so you won't have a problem starting to do things right off, but later on, you will have to manually permit stone types from that screen if you want your masons/stonecrafters to make items out of those specific materials.
It's not altogether good, but on the other hand, you get the ability to forbid even the basic stone for usage, thus allowing you to make statues/blocks/anything out of a specific material with a few keypresses, rather than having to micromanage stockpiles close to workshops to make them use that stone.
[ December 16, 2007: Message edited by: Sean Mirrsen ]