Modern Mining March 2019

DIAMOND MINING

nevertheless decided to proceed as there were a number of advantages to mining Voorspoed from an overall De Beers Group perspective, not least the fact that we knew it was capable of producing some extremely beautiful diamonds from a colour and clarity point of view.” Given the marginal nature of the orebody, De Beers Group realised that it would have to apply a new approach at Voorspoed to ensure the containment of both capital and operating costs. Measures taken included a fit-for-pur- pose design (the offices on site, for example, are all of prefabricated construction), the use of the latest comminution and processing technol- ogy and the recruitment of a very well-educated workforce consisting primarily of people with secondary or tertiary qualifications. The mine – which cost R1,3 billion to develop – was designed to produce roughly 600 000 to 800 000 carats per annum over a life estimated at 10 years via three open-pit cuts and, in practice, this is exactly what was achieved. “There were times when we were operat- ing Voorspoed when we thought that its life might be extended by two or three years and times when we thought it would be slightly shortened but in the end our estimates proved to be very accurate – the life was, indeed, 10 years and we took mining through to Cut 3, as

predicted,” Barton says. “We looked at a fourth cut or even half of a fourth cut and we also con- sidered whether going underground would be feasible. We even brought in some of Anglo’s experts to assist us but no one could come up with a viable plan to make it work, at least from a De Beers’ perspective.” Barton notes that DBCM knew from the start that mining at Voorspoed would be complicated by ground conditions. “This is a kimberlite which is hosted by a very weak country rock – basically mudstone – so we were always going to have some instability in the pit but the prob- lem was more severe than we anticipated. Over the 10-year life, there were in fact around 60 slope and ramp failures. Our guys took it all in their stride and eventually became the best

Above: Phillip Barton at the opening of a Media Centre at Ntsoanatsatsi Primary School in Viljoenskroon in the Free State. The school is in one of the areas from which Voorspoed recruited employees. Left: The Voorspoed diamond mine, seen here, cost R1,3 billion to develop and was opened in 2008.

Open-pit mining operations at Voorspoed.

feature

March 2019  MODERN MINING  33