Surface characters of twin domains and exsolution lamellae in a feldspar crystal: Atomic force microscopy study

Atomic force microscopy (AFM) of a (001) cleavage surface of feldspar crystal reveals exsolution lamellae, wave-like (001) surfaces of the Na-rich lamellae, and surface steps with heights about 0.6 nm and 0.3 nm. The wave-like shape of (001) surfaces of albite twin domains results from surface relaxation of periodic twin domains. Both twin boundary and twin composition planes are parallel to (010). AFM images with 3-dimensional information show surface height difference between Na-rich and K-rich lamellae in some areas, which indicates that the boundaries are semi-coherent along the c axis.