It's most likely jeweler's rouge... mildly abrasive unless you put it on a Dremel buffing wheel them you can make magic with feed ramps, sears, rebound slides, neat stuff like that.
A little bit of it on your cases won't really have any effect on your sizing die, especially if it's carbide. I wouldn't dump it, I'd mix a small percentage (maybe 25%) in with your regular media. It'll make your brass nice and shiny which as you know attracts women. Normally that would be of no use to you but you're going to be ignored for the next year or so. Get used to it.