Sharpening stone among the hardest and the finest to obtain the best sharpness.
Its grit is circa 8000. It is 100x40mm and is protected by a wooden box.
It must be used with special light honing oil (e.g. 55K oil) to lubricate and prevent from clogging.
Since this stone is entirely natural, any colour variation (from white to black), line or porous area do not affect its quality in any way.