Industrial olivine has been carbonated at 175 degrees C, 100 bars in a mixture of supercritical CO2 and an aqueous solution, for 30 min to 12 h in a rocking batch autoclave. Simple settling of the solids recovered after the reaction led to a "fines" fraction and a coarser (residue) fraction. The carbonation extent of olivine was limited to 30% mainly because of the size of the olivine particles used, centered at 138 pm. Observation and characterization of the solids showed that the residue is principally formed by unreacted olivine, whereas the fines consist mainly of carbonates (below 40 gm) with more silica in the range 40106 gm: this segregation with particle size appears promising for separated beneficiation of the silica and the carbonates formed. (C) 2017 Elsevier Ltd. All rights reserved.