>>528511993
I've never actually gotten far enough into the game to build a mine, but judging by the map selection menu it depends on the map.
There's only one where all 3 resources are infinite and I've already played on that, so I chose the one with iron this time. I hope I don't regret it later on, but intuitively I hope that iron sells well (and the production chain for it doesn't look too complicated) so I can just build a big industrial district to finance any stone I'll need for building.