A Defect Study and Classification of Brown Diamonds with Non-Deformation-Related Color

Color Genesis of Brown Diamond from the Mengyin Kimberlite, China

The Mengyin diamondiferous kimberlite cluster in Shandong province is one of the three major sources of natural diamond in China, where many brown diamonds are mined, but the genesis of their color is still controversial. In this paper, studies including microscopic examination, optical properties of orthogonal polarization, low temperature photoluminescence spectra, infrared spectra, Raman spectra, ultraviolet-visible absorption spectra, luminescence of cathodoluminescence, and transmission electron microscopy have been carried out on the uncut brown diamonds and their slice samples to constrain on the color genesis of brown diamond from the Mengyin deposit. The results show that the brown color is dominantly caused by plastic deformation, and some samples are also caused by non-deformation-related defects and inclusions.