I have been running around for quite a while but still haven't found a way or gained a skill that signifies the ability to unlock the urban chests present in iron ore mines. Anyone knows how can we unlock these chests? When I try to open them it just tells me they are locked and she shakes her head.
After you make it to Venice (Outer City District), head to the Old Temple immediately right of the Water Gateway Entrance. Go in, watch the cutscene. You'll learn the skill shortly after.
Once you've got the skill, you can backtrack and get the locked chests.