Characteristics of Diamonds from Cretaceous Kimberlite Placers (Seguela, Ivory Coast)

The Séguéla diamondiferous placers located in the center-west of the Ivory Coast derive from altered kimberlites of the Cretaceous. The mineralogical composition of kimberlites is mainly composed of: olivine, enstatite, phlogopite, amphibole, chromite, Mg - ilmenite , and diamond. Twenty-six (26) diamond samples were respectively observed and analyzed under a microscope and SEM to determine the following morphological characteristics: shape, size, color, weight, fluorescence and inclusions. The most important information is that, Séguéla diamonds are essentially dodecahedral to octahedral in shape . Dissolution is the main mechanism responsible for these different morphological characteristics. The Séguéla diamond prospect produces stones whose weight varies from 0.3 carat to 4 carats. The largest diamond analyzed is 24 carats. Several micro-diamonds are very weakly fluorescent or not. The concentrations of the minerals in inclusion present a color index varying from pale green to black. Some have been identified as garnet, olivine, pyroxene, chromite, spinel, and graphite.