Quote Originally Posted by niftyshaving View Post
Not very hard... The natural mineral is nahcolite with a Mohs hardness of 2.5 (very soft):
https://en.wikipedia.org/wiki/Nahcolite

Any action you get is chemical.
Etching acids are neutralized with baking soda... It is likely to interact with steel in swarf.

The chemical reactions that polish steel are interesting and remind me that Coca-Cola
has one active ingredient: "The active ingredient in Coke is phosphoric acid. Its pH is 2.8. It will dissolve a nail in about 4 days."
This involves tiny nails for sure...

Play with it and other things -- keep notes the tricks of the trade are 'still secret'.

Some hones like Kitayama stones contain Magnesium salts that will dissolve in water
so it is recommended that you do not leave the stone in water for long periods of time.
Kitayama 8000 Grit Water Stone
I think chemically it is magnesium oxide with a hardness of Mohs 6 and steel has a hardness of 4-4.5
Don't forget carbonic acid too. It's in all carbonated drinks.