For those that care about reading ancient threads.

"The Rozsutec gets increasingly finer after intensive use,
probably due to the very hard bond causing the grains
hardly wear or get loose particles. Dressing goes very well
by using a natural Japanese Nagura stone. This smells
strong, but works very well. It creates a slurry that makes
the grinding with the Rozsutec stone much faster. The
slurry gets fairly rapidly much finer."


And just for your info:

Originally the sandstone is blue, but by corrosion the
surfaces, of the plates, the sandstone turns brown.
Therefore, almost all Roszutec whetstones have 2 brown
edges and a blue center band.

These are still being mined by one family in Slovakia

Cheers....

P.S. This is a very versatile stone hone.