Resources from an allied city-state (BNW)

[Carassius]

My city-state ally has two sources of coal - one of which is even located on a mine. I could really use some coal right now. What has to happen before I get some coal? Is there anything that I could do to speed it up?

 

[Mesix]

If one of the sources of coal is unimproved (or has something other than a mine), you should be able to pay to improve the resource. If there is already a mine on a hill with coal, you have to wait for the CS to get the Industrialization technology.

 

[Browd]

And to pay to improve the unimproved coal source, you use the Make A Gift function on the CS's diplomat screen (pay 200 gold to improve a resource).