Natural medium fine Tsuchima nagura stone, assists in the cutting and initial polishing with fine hard stones. 265 gram 45mm cube. These stones are on the harder end of the scale for nagura and will produce a somewhat coarser slurry on a hard stone or raise the mud from a softer stone. Often called "Ocean Blue Stone" these are one of the few Japanese finishing stones mined outside of Kyoto, although the mine is nearly finished. Stones are lacquered to prevent cracking. Do not soak.