Solid Solution

Compositional variation resulting from the substitution of one ion or ionic compound for another ion or ionic compound in an isostructural material. This results in a mineral structure with specific atomic sites occupied by two or more ions or ionic groups in variable proportions. Solid solutions can be complete (with the entire range of compositions possible) or partial (in which only part of the range of potential compositions occurs). For example, olivine shows a complete range of compositions between the end-members forsterite (Mg2SiO4) and fayalite (Fe2SiO4) produced by the substitution Mg2+ → Fe2+.