CaCO 3 is an abundant earth mineral, existing in both hydrated and anhydrous polymorphic forms. It occurs naturally in geological and biological systems as a mixture of its polymorphs, though a phase might predominate depending on physicochemical conditions including temperature, concentration of impurities, and pH. CaCO 3 can also be synthesized by mixing solutions containing Ca 2+ and CO ions or absorbing CO 2(g) in a solution containing Ca 2+ ions. An unstable amorphous phase is instantaneously precipitated in either method. This phase undergoes polymorphic transformations by dissolving and recrystallizing into more stable forms until calcite, which is the most thermodynamically stable polymorph, is formed. CaCO 3 has found extensive applications in diverse process industries. For instance, CaCO 3 particles are inexpensive extenders used in paints and coatings, potential substitutes for pigments such as TiO 2 . 9 They are also used to enhance the opacity, brightness and print quality of paper, 10 and as fillers in plastics and packaging materials. 11 Their use improves the thermal properties and mechanical strength of materials. Further, the use of CaCO 3 particles in personal care products, and biomedical applications have gained traction in recent years. They are used as abrasives and absorbents in cosmetics, and as therapeutic drug carriers. 17-19 However, their application, depends on their morphology, crystal form, size and surface properties. Although small CaCO 3 particles can be obtained from natural sources by comminution, they are rarely monodispersed or impurity free. CaCO 3 nanoparticles can be easily obtained in carbonation methods which involve the absorption of CO 2(g) in a solution of Ca 2+ ions. However, their synthesis in conventional chemical precipitation methods is elusive, particularly in high supersaturation conditions. This is due to the excessive growth of the precipitates. It, thus, informs intense research efforts on methods for the controlled synthesis of CaCO 3 particles and understanding of their growth process. Prior works have investigated the effects of diverse molecules on the nucleation and growth of CaCO 3 crystals. Studies show that the presence of such foreign species influences the growth rate, morphology, and mechanical properties of precipitated CaCO 3 particles. In one example, the hardness of calcite particles is improved by increasing the concentration of amino acids in the crystal lattice. The molecules are incorporated into crystals where they inhibit dislocation motions to enhance hardness. The additive molecules appear as distinct second phase particles, which are incorporated in specific zones and can direct crystal shape changes. This phenomenon has been adapted for the inhibition of CaCO 3 growth and synthesis of relatively smaller particles with high polymorph selectivity. For example, non-ionic dextrans were shown to inhibit the growth of CaCO 3 particles and promote the crystallization of calcite over a metastable anhydrous vaterite phase. In addition, the growth of CaCO 3 crystals is also impacted by the presence and concentration of impurities or additive ions. The literature is replete with reports on the effects of ions such as Na + , Mg 2+ and excess Ca 2+ on CaCO 3 growth. Similar to large molecules, these additive ions are also integrated into the crystals or selectively adsorbed on their surfaces. Though they may inhibit CaCO 3 growth by blocking or poisoning growth sites, the synthesized particles are large, particularly in chemical precipitation methods.