No, not dumb.... I don't mean sprinkel it on your corn flakes, I mean touch it to your tongue, if it tastes salty, sweet, tart, etc it helps guide you as to what it is and how to get rid of it.
My money is that it is calcium / lime scale (crumbles when pinched between fingers, I bet it has a salty taste, and would desolve readily in vinegar)
