Wood definitely works, and for mallets it should be free by the roadside.
In my area ironwood, or hop hornbeam makes the best mallet head, followed by elm, apple, or anything else that is difficult to split. knotty spruce actually works ok, but is too light.
I bring in pieces that are 4 to 8 eight feet long, 3-4 inch diameter, and get out the 1 1/4 ship auger.
I leave them in long lengths and just start drilling holes until I can see that some of the holes are well centered, then I drive in a 1 1/4 octagonal peg and back wedge it. Once the handle is in place, I cut the stiking faces of the mallet head... these should be angled toward the bottom of the handle, as in a turned mallet.
Taking time to round the striking face will help the mallet last longer, I've had mallets last for 5 or more years