Exsolution is the process by which a solid solution separates into two or more distinct phases, typically as a result of cooling. This process is common in minerals such as feldspar and pyroxene, where exsolution can lead to the formation of lamellae or other fine-scale structures. Exsolution is important in mineralogy and petrology for understanding the thermal history of rocks and the evolution of mineral compositions.
Reference: Smith, J. V., & Brown, W. L. (1988). “Feldspar Minerals.” Springer.