Hard mirror finishing stone from Ohzuku mine, not an easy stone to use for inexperienced users, best for razors and knives where hard steel will be worked on, these might not agree with high alloy steels or large carbide alloys. With the use of a nagura, a stone of this hardness and fineness is useful on knives like yanagi or usuba that benefit from a very fine finish on the ura (inside hollow ground side). 

This stone might be scratchy at first and will need to be flattened and the face polished with hard tomonagura or hard nagura. 

202x76x33mm 1398 grams

Asagi:

This aesthetic term refers to the general color of the stone. Typically, Asagi stones are grey, light blue, greyish-blue/green, and tan. They are usually quite clean stones that are on the harder side. However, softer Asagi stones are great for knife polishing.

Goma:

This aesthetic quality looks like tiny black dots, or little sesame seeds in the stone. This quality typically translates to having a fast cutting speed.