Nakayama Asagi Daigokujo Finishing Natural Whetstone 

This is a top quality sharpening finishing stone and if complete it would cost around €2500. Of course, no matter how much it is chipped, the work of the grinding stone itself does not change.

You can tell from the picture that this is a natural stone of the highest quality, especially as it is Nakayama and the fineness of its texture is superior to other honing stones.

Both non-ferrous metals and steel will become mirror-like, but do not apply too much force; just work on the released abrasive grains and at the end relax and sand as if you were crushing the abrasive grains. At this time of year, use warm water, similar to a bath, instead of cold water, as this will bring out the best qualities of the stone.