Kimberlite

Ore deposit type: Magmatic in mafic-ultramafic rocks

Provenance: DeBeers Mine, Kimberley, South Africa

Description: Hypoabyssal kimberlite containing mantle xenocrysts (rounded green diopside crystals and abundant olivine crystals; the latter are mostly visible in thin section). The rock shows abundant macrocrysts of olivine and subordinate orthopyroxene, partially serpentinized and carbonatised, in a groundmass of dominant serpentine, carbonate, spinel (opaque) and perovskite (brown squared crystals with very high relief, abundant, sometimes with spinel inclusions). Many of the apparently opaque grains in the groundmass are in fact perovskite. The macrocrysts are at least in part derived from the fragmentation of mantle xenoliths.