Japanese natural whetstone includes distinguished abrasion power and grain with detail.
Japanese use water for Japanese natural whetstone and sharpen it.
As it uses it, it is a good point that become smooth.
Cloudiness ,mist and haze appear and are beautiful.
It brings around Mt. Atago of Kyoto.
 **Important information **
A natural whetstone is divided into "Honisi" and "Aiishi".
In "Honishi", an appearance is not good, but there are many kinds of stone that between soft and hard.
Abrasion power can be strongly said to be a good whetstone.
However, it takes a dig cost and is expensive.
"Honishi" is a good stone, but an appearance is bad and is expensive.

"Aiishi" is beautiful like man-made stones, and is uniform.
There are kinds of hardness that between soft and medium.
Abrasion power is inferior remarkably.
Because a dig cost is cheap, it is a cheap, beautiful stone, but there is not value as a whetstone.
　A beautiful cheaper stone, and please be careful when there are not only" HONYAMA KYOTO" and information at a production center.
Because we must choose a stone by a name of a mountain and depth of stratum, we do not understand what stone it is only in "Honyama KYOTO".
"HONYAMA" means all of mine in Kyoto.
I must offer many information and details , when I try to sell them.
　I want you to acquire knowledge to ascertain a genuine article.

             **Comparison list of Honishi and Aiishi.

                                    Honishi                           Aiishi

abrasion power             strong                           Nothing

hardness             Hardness of all kinds              soft~medium

Seemliness      Much Honishi is not good              beautiful

a digging cost                  high                                 low

a color of mud
when sharpening   blackish (Iron powder)   whitish (stone powder)

Value as
a whetstone                  enrich                                  poor

         ***Comparison list of Honishi and man-made stone
Question              Natural Honishi whetstone              man-made whetstone

abrasion power
(when starting
grit is the same)              stronger

hardness                         various                                 harder

Seemliness                      funky                                   uniform

haze and mist         many kinds appear     lost forging line and seems uniform mirror.

sharpness                      greater

resistance of rust     hard to be rusted                 easy to be rusted

Does a grain
change as we
polish it?             Yes, become particular            No, uniform grit

Which is more 
congenial
to iron?　         We can confirm it when
                         we put it on rust by easily
                                exfoliating                                    No...


Which
sharpness lasts?    Yes. Let's confirm.

Which is easy
to remove
"Hagaeri"               Yes, of course.             You know ,difficult!

Is it easy to find
a stone
matching us?         Yes,　A characteristic
                                    is infinite.                difficult....that is uniform

Most of a Japanese carpenter use Natural finish whetstone.
We think that man-made stone wins about a rough grit whetstone.
Because they know a good point of stones ,they pay a large amount of price to a stones.
If you come across some stones, you should understand that a Japanese feels it.
Please enjoy sharpening.
 Thank you !