Texture and Genesis of Polycrystalline Varieties of Diamond Based on Phase-Contrast and Diffraction Contrast Tomography

Resumo

Structural peculiarities of several types of cryptocrystalline diamond varieties: carbonado, impact-related yakutite and cryptocrystalline diamond aggregates from kimberlite were studied using Infrared spectroscopy, X-ray diffraction contrast (DCT—Diffraction Contrast Tomography) and phase contrast tomography (PCT). It is shown that the porosity of the carbonado and kimberlitic cryptocrystalline aggregates is similar being in range of 5–10 vol %, possibly indicating similar formation mechanism(s), whereas that of yakutite is essentially zero. Crystallographic texture is observed for some carbonado samples. It is suggested that at least partially the texture is explained by deformation-related bands. Infrared spectroscopy reveals presence of hydrous and, probably, of hydrocarbon species in carbonado.