while it's random, it does tend to cluster. Auger because it hits more often, procs more often. no duh.
With a steel pickaxe, it will proc, just keep smashing away.
Annoyingly, with the auger, the double procs always seem to be when I'm right near the end of the block, and the second one takes out the block below.
Messing up my nice tidy mining ops. tsk.
(for fun, would be nice if that 1 hit would apply to zeds when using an auger. instagib. hee-hee)
I still need more coffee.