I'll probably just end up throwing it out.
Ahh! It's salt! NaCl; members of the animal kingdom have fought and died over access to this resource since forever. It made surviving in times of lean possible via its properties of preserving, which in turn means it has been a key factor in human evolution and prosperity. And it's being mined, and binned by the ton over a fad.
Wipe, and if needed, sand it down until it looks unused again. Then wrap it in waxed paper or some other material used in "artisanal" outlets until passing it on to your enemy. Or use it as salt, because it is salt.