Solid solution

A solid solution is a mixture of two or more solids that have the same crystal structure. A mineral series is a solid solution that is found in nature as a mineral. In general, solid solutions happen when part of one substance can replace part of another without changing how the substances are shaped.

Most solid solutions can be described in terms of "pure" compounds called endmembers. For example, olivine is a solid solution. It has a mixture of iron and manganese cations and orthosilicate anions. The chemical formula of olivine can be written as (Fe,Mn)₂SiO₄ or Fe_xMn_2−xSiO₄. The endmembers are the pure iron mineral fayalite and pure manganese mineral tephroite. These, and any mixture of them, are members of the olivine mineral series.