I ended up with a toishi from Atago Mountain outside Kyoto. I don’t have much more information because the entire conversation with the seller occurred over google translate lol but it’s very hard and very smooth. He let me try it and it felt really really good and was taking off very little steel in very small specs.

A couple questions, how do you know how long to spend on each stone? Is it still about raising a burr or is there a different indicator? Also, can I use my lapping stone to make a slurry instead of a nagura?