Natural whetstone, Natsuya to?

This is a natural whetstone characterized by its red color.

It is likely suitable for medium to fine finishing.
Length: 20 cm
Width: 6 cm
Height: Approximately 3.5 cm
Weight: 1024g
Please note that there may be slight errors in measurements and weight.

AI suggested it might be a Natsuya whetstone, but this cannot be confirmed.
The slurry is a reddish-brown color, and it feels hard yet has good adhesion.
It is not the type that produces a lot of mud.

The red color is very beautiful when wet.
I believe natural whetstones with such beautiful red coloring are rare.
This is a one-of-a-kind item, so if you are interested, please consider it.