Sharpening Stones

[ivan_yulaev]

I was sharpening an old SAK today, and noticed that I was building up sizable metal flakes on my stone. Usually, the flakes are microscopic, and just darken the stone itself. However, these were very visible. Worse, oil would NOT get them out! I had to use a sponge, and when I was done, a few remained and just would not come out. What are these? Bad steel, or is this to be expected?