Piet

in this case yellow stone is not Rozsutec because is not like yours on the picture and is soft like sugar. This stone melts under DMT325. However I have prepared one side on water sandpaper 400 grit, other 1200 grit and they hold this grit. Now I`m even more puzzled. Now I have another 3 hones and no idea what I got. Does grey stone could be some slate, maybe Thuri or similar? It is extra fine grit, very smooth surface.