Iron, but no iron.

[Tutankhamun]

I'm playing a game generated with shuffle. It turned out to be a map of many isles. On my initial island I founded one particular city on an iron source. That gave me access to iron without the need for a mine and I could then build swordmen.

Later on I settled a second isle with another iron source. This one was mined to gain access to it.

Soon after, I found myself at war. The enemy (Huayna Capac) landed on the second isle and proceeded to decimate my second iron source. When that happened, I lost the ability to build iron dependent units in any city in my civilization, despite having a city built on an iron source.

I'm playing standard Civ4, no warlords, patched to the latest release.

 

[BeefontheBone]

Your initial city needs to be connected to the trade network to allow iron access elsewhere. If you traded a source away you'd need to cancel the deal to get it back. Otherwsie, the source might've been exhausted (does that happen to iron? Can't remember).

 

[Tutankhamun]

If you traded a source away you'd need to cancel the deal to get it back.

Cheers. That was it. I gave it away as a gift to a civ that agreed to war with me, to help them along.

I've found that the advisor screens aren't nearly as intuitive as they were in Civ3, so I'd forgotten about giving it away.