sThe Use SAVN_Kimberlite.htm of Vetiver grass in the Revegetation of Kimberlite Spoils in respect to South African Diamond Mining. --- Dr. M. P. S. Berry,
Introduction
Spoils from diamond mining and processing of Kimberlite may be either a coarse fraction of
tailings or a fine fraction known as slimes. Tailings dumps may cover an area of 100 to
200 ha and be as much as 80 meters high with a natural angle of repose of between 30� and
35�. Slirnes dams may cover an area of similar size with walls 20 m high and a
slope of 20�.
Kimberlite by nature is dark in color, easily weathered, high in smectite clays and may be
high in sodium. These chemical and physical characteristics make slopes of kimberlite
spoil dumps highly erodible, hostile for pant: growth and consequently difficult to
revegetate. The problem is further exacerbated by the fact that many diamond mines are
situated in semi-arid environments that are subject to temperature extremes and low and
unpredictable rainfall. Furthermore, some exotic plant species are well adapted to these
harsh conditions and establish comparatively easily to the exclusion of preferred
indigenous species.
Vegetation trials
Vegetation trials with a suite of different indigenous grass species have been
disappointing. Germination tends to be low and seedling mortality extremely high
due to high ground temperatures, inadequate moisture availability and constant erosion of
substrate surface. Some success was obtained where kimberlite spoils were top dressed with
soil to stabilize slope and provide a better growth medium. However, this is extremely
costly and in many instances not possible due to the lack of soil and inaccessibility of
mid-slopes.
Vetiver Trials
Trials with Vetiver have been conducted on both tailings dumps and slimes dumps at
several different sites. In all instances where plants were successfully established,
vetiver has been found to grow vigorously on kimberlite spoils and met both
the mechanical and vegetative requirements for rehabilitation. More particularly:
Conclusion
In conclusion vetiver has been found to have the necessary attributes for self-sustainable
growth on kimberlite tailings dumps and slimes dams. The species is likely to play an
increasingly important role in the rehabilitation of kimberlite spoils. As such nurseries
are being established at several mines to meet expected future demand.
Dr. M. P. S. Berry, Group Ecologist, De Beers Consolidated Mines Ltd., 36 Stockdale
Street, PO Box 616,Kimberley 8300, South Africa. Fax (0531) 807 230