They should be of the finest material possible. In the same way, it is better to use copper for a cauldron than red copper, because it better resists a blow.
The mortars, therefore, used for grinding are stronger and there is less danger of breaking them if they are of fine copper. And for a private home, they do not ring so much and do not make as much noise as those of metal. It is true that those that are of metal ring louder for apothecaries.
Grenades must be made from fine metal