Question for the brain trust.... does this look like the layers are delaminating? Or did this previously belong to a fisherman with very dull hooks? The hard/ fine washita I sold(suspected llw) had some pretty deep grooves in one side(why not move around the stone) and I know for them to get there it took lots of time and someone using lots of pressure. That stone was harder than the ½" smith's "hard arkansas"(I'd call it a true medium, dead between a pike washita and norton hard) and I know it didn't wear quickly because I've sharpened plane irons, axes and lots of chisels on it regularly. This Hindo doesn't really have many visible layers, it seems like a pretty pure stone, but those grooves are on both sides. Seem kind close to the top though to effectively hone hooks on without eventually wearing one in your hand or belly.
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Those look like marks I associate with digging a stone out of a wood base. I have a few stones with scrapes around the bottom that have similar such marks and even made some myself trying to get cemented stones out. I don't know if I've ever see a hindo delaminate, all of mine seem very sound.