I wonder if spawning Materials on Planets is influenced by
- pristine, major, common, ... reserves in the System
- planetary composition (x% metal, x% rocks, type of volcanism)
- inhabitated, not inhabitated
Not sure where I read it but I'm pretty sure that was the idea officially, yes. Heat, material, location, planet type and all that determine the materials.
Not sure if that's actually how it is in practice but I remember that was how it was meant to be at least.
There's quite a few threads about this, as well as various attempts to chart and log the information. As we gather more data we'll be able to correlate.