Abstract: In view of the high-silicon and high-calcium characteristics of a stockpiled magnesite ore from Dashiqiao,Yingkou,a systematic process mineralogy study was conducted using X-ray diffraction（XRD）,X-ray fluorescence（XRF）,and Automatic Mineral Identification and Characterization System（AMICS）. The chemical composition,mineral composition,texture and structure,dissemination characteristics,liberation degree,intergrowth characteristics,and particle size distribution of the ore were analyzed to provide guidance for subsequent beneficiation and purification. The results show that the ore contains 95. 69% MgO,1. 89% CaO,and 1. 72% SiO₂,indicating a high-silicon and high-calcium magnesite. Calcium predominantly occurs in dolomite,while silicon is distributed in pyrope,quartz,amphibole,and clinochlore. Magnesite is mainly in liberated form,accounting for 95. 98%,with a cumulative liberation degree of 97. 38% at the level above 90%,and has a relatively coarse particle size（73. 45% above 74 μm）. Gangue minerals mostly occur as fine-grained disseminated inclusions,closely intergrown with magnesite,and are prone to sliming. The diversity and varying floatability of silicon-bearing gangue minerals cause difficulties in desilication by flotation;Moreover,the similar physicochemical properties and crystal structures of dolomite and magnesite make their flotation separation challenging. Based on the process mineralogy results,a preliminary flotation test using a rough grinding,desliming and single reverse flotation flowsheet was carried out,yielding a magnesite concentrate with 97. 91% MgO,0. 17% SiO₂,and 1. 54% CaO. The findings can provide a basis for the subsequent optimization of flotation conditions.