Help with contaminated Norton 4K/8K
Hi, I recently got serious about honing and bought a Norton 4K/8K from Executive Shaving in the UK. When I realized that it wasn't flat, I also ordered the Norton lapping stone and prep stone from Howard, which won't arrive for several weeks. In the meantime, I'm lapping on a marble countertop with abrasive paper. I live in Italy and I asked the man at the hardware store to recommend an abrasive paper for that purpose: on the back it says "Imperial WOD P600". Is this good?
Second problem: There is obviously metal, or something, embedded in both the 4K and 8K side. On the 4K side, contact with the razor makes a horrible metal-shredding sound. I don't think I had this before I started lapping. Could it be contamination from the abrasive paper? Also, the lapping doesn't seem to touch metal residue in the center of the stone. The 8K side is very smooth but there are one or two points where I am obviously hitting something because there is a rather loud "ting!".
So, my question is. Can this stone be saved by using the Norton lapping stone or some other techique and if so, how much work should I expect to have to do?