Not sure what its made of but it is a white natural stone that will not
only help build up a slurry, but will also "deglaze" the surface of the
stone- taking off the stubborn metal redidue left behind to clean the
stone off. you should use it several times during a sharpening.

It is possible that you are using too much water on the 8000. Dont soak
it, and just squirt a little water on, then use the naugura stone to
build up a slightly wet paste. Add just a drip of water when it gets
dry. Use the nagura stone and rinse with water again when the stone
turns grey from the metal. It should only take a few strokes, maybe
half dozen to make an almost perfectly mirrored surface-- when you hear
the blade squeak across the stone- its done. You should be able to see
your nose hairs.