Why Hagoromo Chalk Is The Best In The World - see the pinned comment

Me thinks this is a really nice, clean, flint and quartz free gypsum, sieved through very fine vibratory screens and the an air separator.

Then they add the kaolin clay - which is very smooth and fine.....

AND I think the binder they are using is rice flour... because it's extremely fine, glutinous and it binds - and smears out smoothly - complimenting the clay and gypsum. Possibly airborn rice dust from flour mills.

The ratios for consistenny and feel, are very important.

I have designed and manufactured chalks, after seeing how BAD the dreadful Chinese stuff can be.

Mine was pretty fucking good...

This is a few notches better.