My current game (Emperor/Big and Small/Standard size and default settings/Normal speed), I hogged half of the continent's copper, but I had no iron. I attacked a neighbor hoping to find iron in his territory. He fled across a channel and we made peace.. but no iron was to be found! Izzy DoW on me and my axes and newly-built cats kill her crap, but I need crossbows against her next wave. I make peace with her ASAP and then trade something like 6 resources (copper, gold, rice, cows, crabs, etc.) AND 4 gpt to Korea just for one lousy iron.
Much later on Khmer (which spread to other islands off the mainland) offered to vassalize, and I said yes because their culture was really hurting me badly at that point, and I needed breathing space. I cancel iron with Korea and get a MUCH better deal with my vassals who had found iron in some godforsaken tundra: I traded them some spare horses and pigs for Iron.
Much later on Khmer (which spread to other islands off the mainland) offered to vassalize, and I said yes because their culture was really hurting me badly at that point, and I needed breathing space. I cancel iron with Korea and get a MUCH better deal with my vassals who had found iron in some godforsaken tundra: I traded them some spare horses and pigs for Iron.