Abstract: This paper describes the separation methods of single mineral with small density difference. Using extremely subtle differences of heavy liquid refractive index in thousandth and ten-thousandth could separate single mineral quartz and sericite. Quartz from felsic mixture separation technology can be used to separate sericite from sericite felsic mixture . Improved heavy liquid separation technology is characterized of fast, efficient and economic. When the heavy liquid of refractive index is 1.577-1.580, the separation purity of quartz can reach 95-99%. When the heavy liquid of refractive index is 1.5895-1.5840, the separation purity of sericite can reach 90-99%.