The Formation of 1.35 nm Stacking Sequences in Heated Products of Clinoenstatites

The structure of pyroxene in a-c section is the arrangement of 'I' beam, which is composed of the stacking of octahedral sheet and Si-O chain layer alternately along a-axis. The distance between two octahedral sheets (or Si-O chain layers, the same below) is near 0.45 nm, and the stacking sequences of pyroxenes, such as orthopyroxene, clinopyroxene and protoenstatite, show that the reversal of the skews occurs for either every two or four adjacent octahedral sheets. However, the odd-layered stacking faults of 1.35 nm blocks along a-axis of pyroxenes from meteorites and anorthosite have been observed since 1985.