I have started casting my own bullets and really enjoy the hobby. I have had great success with making alloys that are the exact hardness I am looking for but ran into something that I can't quite figure out. I was using bullets covered in corundum to lap out a lee bullet sizing die. This worked well and when I was finished with the bullets I tried to remelt them. This grainy looking substance formed in the pot and would not melt. I was able to skim most of it out. My question is what happened and should I try and use the remaining product or just throw the entire batch away? Any advice would be greatly appreciated. Cast on!