Method of processing nepheline syenite powder to produce an ultra-fine grain size product

The method of converting a pre-processed nepheline syenite particulate feedstock with a grain size profile to an ultra-fine grain finish product for subsequent commercial use, said ultra-fine grain product having a grain size of less than about 6 microns, said method comprising:

• (a) providing a dry feedstock with a controlled maximum particle size greater than about 20 microns and less than about 100 microns;
• (b) grinding said feedstock in a dry state by passing said feedstock through a ball mill whereby said feedstock is ground into an intermediate powder, said intermediate powder having a drastically reduced grain size profile than the grain size profile of said feedstock;
• (c) passing said intermediate powder in a dry state through an air classifier using a rapidly moving high speed air stream traveling along a given path to convey said ultra-fine grain product along said path and from said classifier and to allow coarse particulate material including particles larger than said ultra-fine product to be separated from said feedstock by centrifugal force and then expelled from said classifier, wherein said air classifier is a side draft classifier including a main classifying chamber with a vertical blade rotor rejector operated at a high rotating speed below an outlet hood and a lower expansion chamber, said rejector separating said ultra-fine product by allowing said product to pass radially through said rejector together with said high speed air stream, whereby said coarse material is collected in and by said lower expansion chamber;
• (d) collecting said ultra-fine product;
• and,
• (e) returning said coarse material to said high speed stirred ball mill for regrinding.