Solid solution

A solid solution is a mixture formed by dissolving the atoms of an element in a metallic crystal lattice of a second element; the composition of the solid solution is homogeneous and its properties are intermediate between those of several pure constituents. (Garnets are in fact solid solutions with three mineral components).

Two cases are possible:

• either the element is incorporated in the unit cell next to or between two atoms of the principle element: this is an interstitial solid solution;
• or the incorporated element takes the place of an atom of the principle element in the crystal lattice; this is a substitutional solid solution.

Examples of solid solutions

• The plagioclases are continuous solid solutions of which the composition varies from sodic albite, (Si3AlO8)Na, to anorthite, (Si2Al2O8)Ca.
• Alkaline feldspars are a solid solution between potassic orthoclase, (Si3AlO8)K, and sodic albite, unstable at low temperature.