There were a variety of maces in the Middle Ages. They differed in shape of the head (Studded Mace, Flanged Mace, Indian Shishpar), in metals used (wood, copper, bronze, iron), and in length (cavalry usually had longer maces) all of which would determine the final mace weight.
The use of maces in battle was quite common during the Middle Ages, as the weapon was quite inexpensive to produce. Many of the maces on display in museums today are highly decorated for this reason. Though a mace is just a type of club, the image of the spiked mace is what comes to mind for most people.