So (as I tend to do) I've been replaying a previous game from 2200.01.
This time, I was wondering why the heck I'm getting overrun with minerals in the early game. Usually I'm struggling to mine enough, and am unable to build buildings as a result - which is a death sentence for the empire of a popmaxxing tech rusher like me. But even at 2210 now, my minerals overfloweth.
Why?
Turns out this time one of my leaders got the Space Miner trait. It gives a 25% reduction to cost of mining stations. Given each system has maybe 1-6 deposits, that means you save 25-150 minerals per system, and that really adds up in the early game - especially when you're running 2-3 construction ships at once.
This looks like the single most powerful buff you can get in the early game, for those who play wide and expand quickly.