I disagree with the cheese sentiment, mainly because Dwarven cheese is strong and hard like dwarves...
Question - How would an adamantine morning star fair against a stone horse, or stone golem? Great, and the wooden handle wouldn't be an issue. Those creatures aren't as thick as a wall or floor. Stone is hard but adamantine is much harder, a steel morning star would do fine too, it's hardness is better than stone as well, but no one would expect it to cut/smash/pierce through it like cheese.
How would it do against a floor or wall or door? Mediocre. Why? Because it's not designed for the work. Adamantine properties beside, it's piercing properties will chip away at the stone, much like a pick, but not as effective. If a Morningstar designed tool was that effective at breaking stone why aren't miners using them?
How would it do against rope? Terrible, maybe nothing.
If a pick is so great at mining and breaking up rock, why isn't it critting on constructs? Game balance I suppose.
That's why not all adamantine weapons just pierce/cut/smash through everything, it's design and balance. Otherwise the adamantine spiked chain is the way to go.
Torin brought up the most important factor. This is a fantasy world and can break the laws of normal physics. So we are left to imagine the mythical properties of adamantine. Is there some mystical field surrounding the metal that breaks up atomic bonds on impact? Doesn't say so in its description. But it does bypass hardness some how. Or is it just a really strong metal? Answer = DM
Question - How would an adamantine morning star fair against a stone horse, or stone golem? Great, and the wooden handle wouldn't be an issue. Those creatures aren't as thick as a wall or floor. Stone is hard but adamantine is much harder, a steel morning star would do fine too, it's hardness is better than stone as well, but no one would expect it to cut/smash/pierce through it like cheese.
How would it do against a floor or wall or door? Mediocre. Why? Because it's not designed for the work. Adamantine properties beside, it's piercing properties will chip away at the stone, much like a pick, but not as effective. If a Morningstar designed tool was that effective at breaking stone why aren't miners using them?
How would it do against rope? Terrible, maybe nothing.
If a pick is so great at mining and breaking up rock, why isn't it critting on constructs? Game balance I suppose.
That's why not all adamantine weapons just pierce/cut/smash through everything, it's design and balance. Otherwise the adamantine spiked chain is the way to go.
Torin brought up the most important factor. This is a fantasy world and can break the laws of normal physics. So we are left to imagine the mythical properties of adamantine. Is there some mystical field surrounding the metal that breaks up atomic bonds on impact? Doesn't say so in its description. But it does bypass hardness some how. Or is it just a really strong metal? Answer = DM