Black lines/marks in a coticule?
So I recently obtained a small old vintage coticule for pretty cheap. The thing is it has quite a few thin black lines as well as blotchy black lines through it. I assume these are impurities? The stone doesn't appear to be glued, by the way, as there is a very natural looking line (uneven with bits of the darker material imbedded in the yellow coti at the division) dividing the one side from the other.
Anyways, to test it I took an old dull knife I had lying around to it just to test it out (because I wouldn't dare take my razor to it if it might destroy the edge). Worked up a little slurry just honing (no slurry stone after all) then watered it down before it got too thick. Repeated that once more then did a set of strokes with clear water. Just about 10 minutes effort and that knife had an edge like it hasn't seen in a long time!
So, my question is, is this hone serviceable for razors? Will the lines/impurities (?) effect the honing of a razor? It certainly works for knives, and I can put it to plenty of use for that, so its no loss there if it doesn't work for razors. I've also learned that I really like these things so far. Being able to change the cutting properties of the stone with a little slurry or a little water is great. Also they feel very nice to use too! Anyways, thanks for any input!