Atsu Nagura has achieved nearly “Unobtanium” status; I have only seen 3-4 pieces since I became involved with using Mikawa Shiro Nagura for sharpening and honing. Atsu is a relatively coarse nagura, but it is much more consistent than Ban. Historically, its uniformity has lent itself for use in all modes of sharpening, as well as sword polishing.
