Dec 11, 2019 Gypsum Powder Milling Process. Phase 1 Crushing the raw materials. Potash Feldspar blocks are crushed by the crusher to the size of 15mm-50mm and into grinding mill. Phase 2 Grinding. The crushed coarse Potash Feldspar are sent to the storage hopper by the elevator, and then sent to the grinding chamber by the feeder for grinding.