TEM and SFM of exsolution and twinning in an alkali feldspar

Transmission electron microscopy (TEM) reveals exsolution lamellae in a cry ptoperthite; their spacing results in a greenish-yellow iridescent color. H igh-resolution TEM images show that the boundaries between Ab-rich and Or-r ich lamellae are semi-coherent along the b axis. Scanning force microscopy (SFM) of a (001) cleavage surface reveals exsolut ion lamellae, wavelike (001) surfaces of the Ab-rich lamellae, and surface steps with heights of similar to 6.6 and similar to 3 Angstrom. The wave-li ke (001) surfaces of albite twin lamellae may result from surface relaxatio n. Surface height differences between Ab- and Or-rich lamellae in some area s indicate a semi-coherent boundary along the c axis.