What kind of mortar and pestle is most food safe? Even after conditioning/seasoning one can expect microscopic chips from using a mortar and pestle.

Intuitively it seems that a metallic M&amp;P would be more inclined to shed not so healthy chips, in contrast to a combination of a hard mortar (granite) and a (food safe) soft pestle (wood) whose chips are non toxic.
A granite mortar and granite pestle; this combination will do everything.

The granite is hard and dense and will not chip under regular usage.

You need to remember that the mortar and pestle must be harder than what you need to grind.

Serious Eats Mortars and Pestles is a good read.