Naniwa Premium Diamond Sharpening Stone #10000 – Limited Edition

If you've ever wondered what a truly mirror finish looks like, this is the stone that gets you there. The Naniwa Premium Diamond Stone #10000 sits at the very top of the finishing range — this isn't a stone for putting an edge on a dull knife, it's the one you reach for once the edge is already sharp and you want to take it somewhere most stones can't go. At #10000 grit, it's specifically built for polishing the hardest Japanese steels and modern powder alloys, the kind of steel that would otherwise chew through a softer finishing stone before it even got going.

What makes this one worth the price tag is the sintered diamond surface. Unlike a bonded abrasive stone that can flake or wear unevenly over time, the diamond particles here are fused into the surface, so you get consistent cutting action stone after stone without worrying about it degrading on you. The feel under the blade is smooth and controlled rather than grabby, which matters a lot at this grit — you're removing almost nothing with each pass, so consistency is everything.

It's genuinely low-maintenance to use: no soaking required, just wet the surface with water and go. It also ships with a dressing stone, which is worth actually using regularly rather than leaving in the box — keeping the surface flat is what lets a stone this fine do its job properly over the long run.

Worth noting: this is a finishing stone, not a workhorse. You'll want a full progression underneath it (rough to medium grit) before this one comes into play — trying to jump straight to #10000 on an unsharpened edge will just waste time and diamond surface. But for chisels, Japanese planes, and knives where you want that final glassy edge and mirror bevel, it's hard to beat.