Abstract
Needle-shaped crystals found in samples of aynthetic diamond grits have boen examined by X-ray diffraction, optical methods and scanning electron microscopy. It 18 shown that thew crystals re cyclic twins with a morphology hitherto unreported. The crystal habit of theae cyclic twin crystals rssults from pronounced {1OO} faceting, characteristic of synthetic dinmond, in addition to {111} growth feces. thereby producing the needle-shaped crystals observed. This is different from the five-branched star cyclic twin crystal habit previouly found in both natural and synthetic diamond grits and in which only {111} facets am present.