Abstract
Consideration of possible transformation mechanisms in natural ZnS suggests that ideal 2H wurtzite may transform toward a sphalerite structural state through isolated edge dislocations in individual hexagonal close-packed layers. Complete transformation to ideal 3C sphalerite appears to involve two distinct steps, a continuous transformation to an intermediate disordered layer sequence followed by a final discontinuous transformation; the latter is possibly only realised through recrystallisation. The 2H → 3С structural transformation is illustrated by study of a sphalerite from Thomaston Dam, Connecticut, which yields X-ray diffraction patterns with broadened and diffuse reflections along reciprocal lattice rows with h − k ≠ 3n (equivalent hexagonal indices). This diffraction effect may be regarded as diagnostic of sphalerite (or sphalerite-like ZnS) which has formed by inversion of a more wurtzitic precursor.
In contrast, solid-state transformation in ideal 3C sphalerite is limited to the formation of deformation twins ([111] twin axis). This is illustrated by X-ray diffraction study of a deformed sphalerite from Austinville, Virginia.