Are these polishable?

First one looks like schorl tourmaline in a mica-type schist. Try flaking at the gray and black areas with a penny - if the gray is schist, you'll be able to flake off bits of it (and if the black is something softer like coal, you may be able to flake off some bits of that, too). The second could be marble or limestone with some mica (metal is possible, though) - if you put a drop of pool acid (muriatic acid) on the light colored part, if you see bubbles develop inside the bubble or if it fizzes, you'll know it is likely limestone or marble (if you can flake off a small piece of the silvery stuff and can see through it with a strong light in back, it is mica). The translucent portion in the last photo could be beryl or quartz, both are possible in MD, but I haven't seen specimens of either that are embedded in matrix such as your piece.

The ability to get a polish is going to depend on how different are the hardnesses of the stones, especially if you tumble-polish them. For example, if the first piece is indeed tourmaline in schist, the schist is going to either undercut severely or wear away entirely, leaving you with polished tourmaline shards (the schist is much softer than tourmaline). Grinding and polishing on wheels is possible, but requires a bit of experience/skill, IMHO.