An electron microscopic study of some twinning and exsolution textures in microcline amazonites

An electron microscopic study of the twinning and exsolution textures in one hydrothermal and two pegmatitic amazonites from southern Norway is reported. From observations of three types of interfaces: between twins, between domains twinned on different laws and between Na- and K-feldspar domains, perthitic textures involving low albite lenses up to 10 μm long in a twinned microcline matrix are shown to result from exsolution from the triclinic phase. Complex twinning on albite and pericline laws is suggested to be the result of strains induced by exsolution. Other textures, involving the late introduction of Na at low temperature in a pegmatite and the occurrence of Pb-rich and plagioclase crystallites in a hydrothermal amazonite, are described.