About the issue I mentioned earlier - here is a later save game, that points to some problems related to mountain mines:
1. As before, the city of Tingis is not able to build Turquoise mine or any Turquoise-related cultures (like Moche, though it does have a peak and turquoise in the vicinity.
2. The city of Thaenae is not able to build the Jade Mine or the Jet Mine (I have Refining tech to build it and Obsidian + Jade in city vicinity). The Jade near that city wasn't there initially, it got discovered a dozen turns before.
3. Same Jade-related thing with the city Carthago Nova. It also can't build a Tin mine, even though it has Tin (again, on a mountain) in the vicinity.
4. City of Sabratha can't build a Copper Mine, and again, it has copper in the vicinity on a peak tile.
Looks definitely like a bug with vicinity bonus calculation in relation to mountain tiles...