Michiel, Yea that was the one that got away
We should do a trade for another...
Jack, the black swarf is metal. On a Shapton letting it accumulate will just glaze the stone over. Not worth keeping. On the Snow white, you could keep it if you are contemplating using it again in the near future. I wouldn't worry about it and just rinse it off or put the mud on some paper or balsa if you want to save it for reuse.