Process for the production of a precipitated divalent metal ion carbonate product from a divalent metal ion carbonate which was recovered from waste, the precipitated divalent metal ion carbonate product having an improved brightness, the process comprising the following steps of: (a) providing a low-purity divalent metal ion carbonate material having an ISO brightness R457 of less than about 90%, as measured according to ISO 2469, the divalent metal ion carbonate material being recovered from waste; (b) calcining the divalent metal ion carbonate material of step (a) in order to obtain a divalent metal ion oxide; (c) slaking the divalent metal ion oxide obtained in step (b) in order to obtain an aqueous suspension of a divalent metal ion hydroxide; (d) carbonating the aqueous suspension of the divalent metal ion hydroxide obtained in step (c) with a carbon dioxide containing compound in order to obtain precipitated divalent metal ion carbonate particles consisting of clusters or agglomerates of fine particles, the fine particles having a particle size of > 10 to 500 nm and a specific surface area of 5 to 50 m 2 /g; (e) post-treating the precipitated divalent metal ion carbonate particles consisting of clusters or agglomerates of fine particles obtained in step (d) to obtain fine discrete precipitated divalent metal ion carbonate particles having a particle size of > 10 to 500 nm and a specific surface area of 5 to 50 m 2 /g; (f) mixing the fine discrete precipitated divalent metal ion carbonate particles obtained in step (e) with an aqueous suspension of divalent metal ion hydroxide that was obtained by slaking high-purity divalent metal ion oxide having an ISO brightness R457 of at least about 94%, as measured according to ISO 2469, in order to obtain a resulting reaction mixture; and (g) carbonating the resulting reaction mixture of step (f) in order to obtain the precipitated divalent metal ion carbonate product having an improved brightness as compared to the precipitated divalent metal ion carbonate particles obtained in step (d). (a) providing a low-purity divalent metal ion carbonate material having an ISO brightness R457 of less than about 90%, as measured according to ISO 2469, the divalent metal ion carbonate material being recovered from waste; (b) calcining the divalent metal ion carbonate material of step (a) in order to obtain a divalent metal ion oxide; (c) slaking the divalent metal ion oxide obtained in step (b) in order to obtain an aqueous suspension of a divalent metal ion hydroxide; (d) carbonating the aqueous suspension of the divalent metal ion hydroxide obtained in step (c) with a carbon dioxide containing compound in order to obtain precipitated divalent metal ion carbonate particles consisting of clusters or agglomerates of fine particles, the fine particles having a particle size of > 10 to 500 nm and a specific surface area of 5 to 50 m 2 /g; (e) post-treating the precipitated divalent metal ion carbonate particles consisting of clusters or agglomerates of fine particles obtained in step (d) to obtain fine discrete precipitated divalent metal ion carbonate particles having a particle size of > 10 to 500 nm and a specific surface area of 5 to 50 m 2 /g; (f) mixing the fine discrete precipitated divalent metal ion carbonate particles obtained in step (e) with an aqueous suspension of divalent metal ion hydroxide that was obtained by slaking high-purity divalent metal ion oxide having an ISO brightness R457 of at least about 94%, as measured according to ISO 2469, in order to obtain a resulting reaction mixture; and (g) carbonating the resulting reaction mixture of step (f) in order to obtain the precipitated divalent metal ion carbonate product having an improved brightness as compared to the precipitated divalent metal ion carbonate particles obtained in step (d).