After they've given me the gas.
Viewing post in The prospectors are bugged
Alright, at least you're not missing any content with them, and you can complete the main storyline. That's a relief!
If you tell them that they should not build the mine, they are supposed to move away. Maybe that's not clear though, or they're not behaving the way we intended. We'll add it to our bug tracking system.
Thanks again! :)