Which preposition to use with goldmines

in Occurrences 1%

In Luzon, for instance, Hernando Riquel stated that there were many goldmines in several places which were seen by the Spaniards; "the ore is so rich that I will not write any more about it, as I might possibly come under a suspicion of exaggerating; but I swear by Christ that there is more gold on this island than there is iron in all Biscay."

Which preposition to use with  goldmines