Abstract: Method for industrial manufacture of pure (precipitated) CaCO3 comprising providing at least one naturally occurring carbonate bearing rock and comminuting said rock to increase its surface area. In a first reaction zone (R1) the comminuted carbonate bearing rock is contacted with water and CO2 at a pressure higher than standard pressure, at a temperature in the range 30-500° C. and at a pH lower than 5 to thereby dissolve the carbonate. Dissolved material is conveyed from the first reaction zone (R1) to a second reaction zone (R2) held at a lower pressure than the first reaction zone and a pH higher than that of the first reaction zone, the presence of H+ ions in first and second reaction zones being caused by the reaction between CO2 and water. In the second reaction zone the calcium carbonate is precipitated at a pH higher than 5.

Abstract: Method for industrial manufacture of pure MgCO3 comprising providing an olivine containing species of rock, to comminute the olivine containing species of rock to increase its surface, to contact the comminuted olivine containing species of rock with water and CO2. The process is conducted in at least two steps, namely a first step (R1) at a first pH where a dissolving reacting as represented the equation: Mg2SiO4(S)+4H+=2Mg2++SiO2(aq)+2H2O, takes place. Then a precipitation takes place in the second step (R2) at a higher pH as represented by the equations: Mg2++HCO3?=MgCO3(S)+H+, and Mg2++CO32?=MgCO3(S), the presence of HCO3? and H+ ions mainly provided by the reaction between CO2 and water.

Abstract: Method for industrial manufacture of pure MgCO3 comprising providing an olivine containing species of rock, to comminute the olivine containing species of rock to increase its surface, to contact the comminuted olivine containing species of rock with water and CO2. The process is conducted in at least two steps, namely a first step (R1) at a first pH where a dissolving reacting as represented by the equation: Mg2SiO4(S)+4H+=2Mg2++SiO2(aq)+2H2O, takes place. Then a precipitation takes place in the second step (R2) at a higher pH as represented by the equations: Mg2++HCO3?=MgCO3(S)+H+, and Mg2++CO32?=MgCO3(S), the presence of HCO3? and H+ ions mainly provided by the reaction between CO2 and water.