Sand
If you grind a stone down to more than just a few pieces, it will become sand. Stones that get broken up enough will become sand, and you pick up a few grains in your hand.
さ, しゃ
すな
None
After breaking up your stone into sand, you fetch your special sand saw (さ). A few bits are still too chunky, so you'll have to use a sand saw now.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.