You need a hard impact surface, mass isn't enough because its too malleable.Yeah, that is pretty much I could find. Utterly terrible for bladed weapons and armour, but could be decent for blunt weaponry. However, the softness means that they would deform or otherwise get damaged with every hit and therefore require either constant maintenance or replacement.
You haven't reached that point yet.
Lead hammer or mace with granite moulded around the metal would do fine for a maul
You could also look into a Meteor Hammer. for Fancy Shit
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For a simple warhammer or mace dents are not much of a concern; they can be easily fixed and don't really impact the effectiveness of the weapon much. However, silver weapons would still not be a good idea. The density of the metal used does not actually affect the usefulness of a mace or warhammer; it is the weight that does that.
In dwarf fortress you have such an effect because it models silver warhammers as having heads the same size as those of other materials, and thus being much heavier. However, in real life, very heavy warhammers and maces are impractical due to tiring out the user and the momentum making them harder to use effectively. Any silver weaponry would have the head reduced in size so as to have the same weight as non-silver weaponry.
Density does matter though, a denser hammer is better at smashing through bone than a less dense hammer of the same mass.