Calcium isotopes are fractionated during inorganic precipitation from aqueous solutions according to their relative mass differences. The magnitude and sign of isotope fractionation depend on the composition and structure of the solid and the physicochemical conditions of the aqueous environment. The first part of this chapter focuses on Ca isotope fractionation during precipitation experiments at well-defined conditions, where results for Mg, Sr and Ba are included for the discussion of fractionation mechanisms. Different conceptual models for Ca isotope fractionation between carbonate minerals and aqueous solutions are discussed in the second part. The following parts of this chapter illustrate Ca isotope variability found in inorganic minerals from natural environments and the Ca isotope fractionation related to ion diffusion, exchange and adsorption in aqueous systems.