As I wrote before, a stone I bought from a reputed hone dealer had a toxic suji^?, one that made it mostly unusable. I tried the recommendation of digging it out with a nail or somesuch, but the inelegance, and temporariness, of the solution bothered me. Then, lo and behold, I remembered: my landlord/neighbor owns a stone statuary shop! I went to him, and he did indeed have the space, tools and skill to cut my stone.

The suji was located in such a way that a single cut should solve all my problems, and when I showed it to him he knew just what to do.

He cut straight through the suji, using the kerf of the saw to grind as much of it out as possible.

Afterward, I ended up with a stone and a nice big tomonagura. But looking inside, I got a glimpse of just how bad this problem really was.

Those black cracks are the suji, and they extend deep, deep into the stone. From here, it should be little trouble to expose them and clean them out, leaving me with an excellent stone. Indeed, I already have one--I've tried honing with it and yes, the problem with grittiness and suji is gone, since there is no exposure on the face.

So there you have it, one way to deal with suji...cut the nasty things out!