The type of metal doesn't matter, but I am pretty sure I can't pay for a silver/gold mine. I can provide cavebulbs, pearls, linen cloth, bricks, any amount of other less valuable forageables/commodities, q60 soil, q70 clay (both in a limited amount), metal bars, q40+ sausages and low q wine.
A mine in this area or near this area is preferrable:
