Coherent elastic energies of exsolution boundaries in peristerite and böggild intergrowths

Elastic energy calculations based upon the coherent model of Willaime and Brown [Acta Cryst. A30, 316–331 (1974)] have been carried out for some exsolution textures in peristerite and Böggild intergrowths. For peristerites it is demonstrated that substitution of K for Na moves the orientation of the exsolution lamellae from (08 (overline {text{1}} ) ) to about ( (overline {text{1}} ) , 21, (overline {text{2}} ) ) in agreement with observations. An electron microscope study of exsolution textures in labradorite and andesine plagioclases has been carried out and information about small structural differences in these lamellar structures has been obtained from elastic energy calculations.