Mineralization heterogeneous nucleation

Adsorption influences the reactivity of surfaces. It has been shown that the rates of processes such as precipitation (heterogeneous nucleation and surface precipitation), dissolution of minerals (of importance in the weathering of rocks, in the formation of soils and sediments, and in the corrosion of structures and metals), and in the catalysis and photocatalysis of redox processes, are critically dependent on the properties of the surfaces (surface species and their strucutral identity). 

Enhancement of Heterogeneous Nucleation by Specific Adsorption of Mineral Constituents... 

Stumm, W., F. Furrer, and B. Kunz (1983), "The Role of Surface Coordination in Precipitation (Heterogeneous Nucleation) and Dissolution of Mineral Phases", Croat. Chem. Acta 56, 593-611. 

The geochemical fate of most reactive substances (trace metals, pollutants) is controlled by the reaction of solutes with solid surfaces. Simple chemical models for the residence time of reactive elements in oceans, lakes, sediment, and soil systems are based on the partitioning of chemical species between the aqueous solution and the particle surface. The rates of processes involved in precipitation (heterogeneous nucleation, crystal growth) and dissolution of mineral phases, of importance in the weathering of rocks, in the formation of soils, and sediment diagenesis, are critically dependent on surface species and their structural identity. 

At some distance close to the mineral surface, the saturation index (SI, IAP/Xsp) of pyromorphite must be greater than zero to allow local super saturation and precipitation. The question is whether this is a heterogeneous nucleation/ surface precipitation reaction or a dissolution homogeneous nucleation reaction. 

Effect of sie on heterogeneous nucleation. Figure 17 shows an example of a mineral dust particle coated by hygroscopic salts. The deliquescence/efflorescence hysteresis cycle is reduced due to heterogeneous nucleation when foreign material, such... 

We must now consider the important question of the probability of these mechanisms taldng place in biomineralization. It is often implicitly assumed that the main function of the matrix is to act as a template for mineral development through the control of crystal orientation and structure, but as we have discussed previously this is not necessarily correct since the matrix may serve simply as an energetically favourable site for heterogeneous nucleation, or as a means of volume constraint, or as a framework for structural support. Thus the bulk mineral is often observed to be composed of crystallites interlaminated and virapped with organic sheets and it is often not at all clear what function the matrices serve. 

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