I have usually been lucky buying stones. I like my Iyo. It is not a natural version of Shapton 1000, and so I don't use it often for sharpening. I use it as a scrubber to clean stones and as a nagura on some stones ( 4-5k range) as the "grit" seems to break down quite fine and quick.

It makes a good third stone for keeping your middle and finish stone up and running. mine is clean and nearly all white. For a purists approach it can do the coarse work but not as well as synthetic water stone