Black walnut is very common here. There used to be a rough old local codger that would de-hull walnuts and crack them with a hammer on a chunk of railroad rail. He loved the nuts, and did this every fall. He was in his 70s when I met him. He made a living as a carpenter, auto mechanic, a little farming. Bragged he never wore a pair of gloves his entire life even in winter. His hands were huge, knarly, and cracked. Each fall they would be stained brown a couple months from the walnuts, until the stain wore off.
Intresting, though, I met him while playing music. Those huge hands of his would glide effortlessly up and down the neck of a guitar playing western swing music. Never played single notes, always played a full chord for each note. Died a few years ago.