Dry rock in the garage, had DE dust on some of the rocks...

I have some super old dry rock, like 15+ years old. My wife accidentally dusted DE around the buckets where I had the rock stored and got a little bit of that stuff (diatomaceous earth) on some of it.

It wasn't much. Maybe one or two rocks got a small amount of DE on them, but now I'm not sure what I should do. Can I just dust it off and rinse the rocks really well? Should I toss the pieces that came into contact with it? Or is DE harmless enough that a good rinse is all they need?

I've been saving these rocks forever for my next tank... whenever that happens. They're old Fiji rock and some nice branching pieces, so I'd really rather not throw them away if I don't have to.