Ore deposit type: Magmatic in mafic-ultramafic rocks
Provenance: Kimberley (South Africa)
Description: Mantle peridotite xenolith from the famous Boschoff Road site, where waste materials from the processing of Kimberley kimberlites have been accumulated. It is a harzburgite, made mostly of anhedral olivine (brownish where altered, dark green on fresh surfaces) and orthopyroxene (whitish where altered, with vitreous luster and evident cleavage), with lobate outlines, associated with minor pyropic garnet (pinkish purple) and accessory clinopyroxene (emerald-green millimetric crystals). Mantle xenoliths are common in kimberlites and lamproites because they are sampled, similar to diamonds, during the rapid ascent of the magmas through the lithosphere. Occasionally, they are diamondiferous.