Patent ID: 8070080

Claim:
A method of converting a pre-processed substantially dry nepheline syenite feedstock with a particle size profile and a maximum particle size greater than 20 microns into an ultra-fine grain finished product in the form of a nepheline syenite powder with a maximum particle size of less than 10 microns, said feedstock having a first hardness, said method comprising: (a) passing said feedstock vertically downward through a vertical continuous, high speed stirred ball mill having stirring arms rotating at a selected speed in a vertically extending chamber filled with a ball-like grinding media having a second hardness substantially greater than said first hardness whereby said feedstock is ground into an intermediate powder having a particle size profile less than the particle size profile of said feedstock; (b) passing said intermediate powder through an air classifier to remove coarse particle material including particles larger than said ultra-fine grain finished product; and, (c) collecting said ultra-fine grain finished product.