If it can be determined that two faceted diamonds came from the same piece of rough, romantic value is added to the stones. X-ray topography and cathodoluminescence (CL) tomography were used to prove that a round brilliant and a pear-shaped brilliant were cut from the same piece of rough. With these techniques, the internal imperfections and inhomogeneities that reflect the distinctive growth history of the original diamond crystal can be visualized. X-ray topography is a powerful tool for imaging the distribution of lattice defects; CL tomography is more sensitive for detecting faint chemical inhomogeneities. By combining the two methods, the sophisticated gemologist can view both physical and chemical characteristics of a crystal, and thus its growth history, and use this information to fingerprint a given stone.


Appears on pages 270-280