The morphological characteristics of diamonds from the Ekati property, Northwest Territories, Canada

Examination of exploration diamond parcels from 13 kimberlites on the Ekati Diamond Mine™ property revealed abundant octahedra and dodecahedra, significant numbers of cubes (fibrous and non-fibrous), minor cubo-octahedra and aggregates, and rare macles and pseudo-hemimorphic crystals. Some octahedra have a fibrous diamond coat. The diamonds are predominantly colourless or brown with minor yellow and very few other colours. A striking feature of the diamonds from all 13 localities is their mixed character, evidenced by the variety of colours, crystal forms and surface textures and as previously documented for Siberia (Orlov, Yu L., 1977. Mineralogy of the Diamond. Translated from the Russian language and published by Wiley, New York. Original (1973) published in Russian by Izdatelʹstvo, Nauka, USSR.) and by Robinson (Robinson, D.N., 1979. Surface textures and other features of diamonds. PhD thesis, University of Cape Town, South Africa.) for the Kaapvaal craton. This mixed character can be largely accounted for by variations in the proportions of components (termed building blocks [BB]) of diamonds with similar characteristics that are represented at each of the 13 localities. These descriptions reveal three very strongly developed regional associations. The highest proportion of both colourless octahedra and total octahedra is present in the northwest part of the study area, which includes the commercially exploited kimberlites, Panda, Koala and Beartooth. In contrast, diamonds in the centrally placed kimberlites Arnie and Mark are dominated by opaque fibrous cubes. In the southeast part of the study area, the diamonds from four kimberlites including Misery are characterized by dodecahedra that are dominantly brown. The most southerly pipe, Piranha, is unique within this group of 13 kimberlites in that it has a high proportion of cubo-octahedra and of colourless cubes.