What makes ore spawn at any level?

[xmanic189]

I'm just curious as to what makes ore spawn at any level. I'm not sure whether it's a mod or something else that changes the generation of ore. If it is a mod please tell me which mod does that . If it's not then what is it? I'd like to be able to do that to my own personal modpack. I've gone through all the mods in hexxit and read about all of them but I've not found anything about it.