A good tough but softish hammerstone works well for spalling, as do big moose antler billets or big copper boppers. If you have sandstone in your area, a smooth rounded one from a creek or river makes a good hammerstone. If the hammerstone is too hard, it tends to shatter and cone out the core. Match the size of the hammerstone to the size of the core, one about the size of a baseball is usally good for knocking off arrowhead-sized flakes.
