I have seen one time before stone like that, it was also Nakayama.
feels very soft but very very fine. Make green mud/slurry.
And feels super nice ! On everything knives razors and tools
Very light yellow color, what they call in Japan lime yellow. Most sought after Nakayamas out there !
Quite big and thick koppa.
But still much cheaper then same full size Nakayama Kiita, that will go for 5, 6 times more .
Collector Grade !
MAX size: 170mm 110mm 30mm