Abstract: A process of removing iron impurities from ores, particularly useful for removing stains of iron impurities adhered to silica sand particles, comprises grinding the ore, washing and desliming the ground ore to remove the major part of the clay-type binder, attrition-scrubbing the deslimed particles to release further amounts of binder therefrom, washing and desliming to remove said binder, drying and heating the ore particles, treating the hot particles with a chemical agent suitable to conver the iron impurities into water soluble iron compounds, attrition-scrubbing the hot suspension of chemically treated particles to release the stains of iron impurities, and washing with cold water and desliming to recover the purified ore particles.

Abstract: A process of purifying silica sand comprises grinding sandstone, washing and desliming the ground sandstone to remove the major part of the clay-type binder, attrition-scrubbing the deslimed sand particles to release further amounts of binder therefrom, washing and desliming to remove said binder, drying and heating the sand particles, treating the hot sand with sulfuric acid to convert the iron oxides, ferrosilicates and ferro-aluminous impurities into water soluble compounds, attrition-scrubbing the hot suspension of the chemically treated sand to release the strongly adhering stains of said impurities, washing with cold water and desliming, conditioning the sand suspension with fatty acids or petroleum sulfonate collectors, a polyalcohol frothing agent and, if necessary, a mineral acid to bring the pH to from 1.5 to 7.