Defect characterization in natural diamonds by laser-light-scattering microtomography

Abstract

Scanning microtomography using scattered laser light has been employed in a study of defects in small blocks of different types of diamond. Local changes in refractivity caused by various kinds of imperfections could be mapped. In relatively perfect yellow diamonds the scattered-light intensity distribution was related to growth zones, as was verified by stress-birefringence microscopy and cathodoluminescence. Scattered-light images of dislocation lines were also observed. In some diamonds it was found that {100} growth sectors showed a lower scattering intensity than the adjacent {111} sectors. Brown anisotropically scattering diamonds gave an inhomogeneous striated scattered-light distribution, not related to growth zones. A diamond with knots showed local differences in scattering intensity for the misoriented crystal volumes.