I am with Janglur on this. I just did approximately three dozen embarks on areas with "multiple" deep and shallow metals over the course of several hours and did not once see a single embark with more than one meaningful metal (iron, coal, gold/aluminum/platinum). It's getting pretty ridiculous. So, I'm going to endeavor to mod this.
I don't think it's completely possible. There's a FREQUENCY tag on each stone entry, but from what I remember that controls the relative likelyhood of appearance, not the absolute.
Is the underscored number here the frequency value?:
[ENVIRONMENT:SEDIMENTARY:VEIN:
100]
If so, do you know if it can go above 100?
You could add a bunch of redundant iron stones, or whatever.
So instead of one magnetite, you'd have a magnetite in granite, or whatever, and a magnetite in some other place, like in limestone or something.
Just keep stacking them until you have reached your preferred frequency.
It should work in theory.
Definitely going to have some of this. I assume you'll need to rename each one, though? Or can the engine handle having multiple magnetites?
Anyways, here's my goal: I want to ratchet the frequency of the various 'fluff' minerals way, way down -- these are really the largest offenders because the world gen obviously counts them as a metal (I saw one embark with multiple deep and shallow metals listed, but no metal at all, just junk), then add new lesser deposit versions of pretty much every metal ore with increased (200? 300?) frequency but only appearing in small clusters, not veins. Finally, I plan on making some metals appear in more types of rock. Coal is found frequently in metamorphic layers IRL, iron, specifically magnetite, has been found in pretty much every type of rock (albeit not in as large a quantity as found in sedimentary banded iron deposits), native copper and malachite should be present in sedimentary rock, etc.
The idea is to make minerals more frequent but appear in lower quantities. Right now, if you have access to a type of ore you have TONS of it; doubly so if that ore appears in clusters like magnetite does -- then you're practically drowning in it. (One embark had 36,000 magnetite according to DFprospector, and looking at the map in DFreveal showed it pretty much covering entire layers with magnetite.) However, if you don't have it, you have none at all and it isn't even worth looking for.
In the end while the current approach will work nicely once the caravan arc is done and you can actually import what you lack (as well as tweaks such as making mineral distribution far finer so you don't end up with entire continents that have the same minerals in all areas) but at the moment it simply leaves the game unplayable if you're trying to gen a .31.19 world.