Direct Observation of Stacking Faults in Wollastonite

Abstract

Wollastonite is well known to have diffuse streaks on k odd level in its X-ray diffraction photographs which have been said to be due to stacking fault with displacement of b/2 in stacking along the a direction (JEFFERY, 1953). The stacking fault is directly observed by high-resolution electron microscopy. In the electron micrograph frequent stacking faults are observed in some places (faulting density α=0.4~0.6), but the density varies very much from portion to portion. A dislocation is observed in two dimensional lattice image. Electron diffraction of wollastonite indicates some features which were not found in X-ray photographs; faint streaks along a * on k even levels of (hkO) reciprocal lattice plane and faint streaks along c * on k odd levels of (Okl) reciprocal lattice plane and fine structure of the streaks along a * on k odd levels of (hkO) reciprocal lattice plane.