Pb block to Pb powder? Is there any chemical way. The only way I can think of right now is the mechanical with a hammer, or melting it down and throw it on water.
Dont set your heart on this, I'll tell you straight out, its only a logical guess.
But could you salt the lead with an acid, then reduce it back to the metal with a base to steal the anion?
PrimoPyro
Vivent Longtemps la Ruche! STRIKE For President!
A very fine file should do it. Lead is a very soft metal.