Modern Mining April 2015

COUNTRY FOCUS – ZAMBIA

from a few centimetres up to 2 m in thick- ness, are what we target – everything else is waste,” he said. “In the Chama pit, the TMS dips at 16 deg to the south and south-east and is cross cut by the pegmatites vertically. The pit slowly migrates as we follow the TMS and, in fact, we’re now busy with our fourth highwall pushback, which will extend the pit by a fur- ther 75 m to the south-east.” He pointed out that the emeralds that form within the ore (reaction zone) tended to occur in pockets. “The result is that you have good times and bad times – but they tend to even out,” he noted. Grade can vary considerably but averages out to 300 carats per tonne for the Chama pit. Gessner added that most of the rock han- dling in the pit related to the waste with ore production only accounting for about 8 000 tonnes a month. “The waste stripping is a 24/7 operation carried out both in-house and with the assistance of a contractor whereas we do the ore mining ourselves and only during day- light hours – because we need good visibility to detect the emeralds, which are normally encrusted with schist, and for security reasons. Although excavators are used to open up the contact zone, essentially this is a manual oper- ation by teams of chisel men – watched over by security personnel and geologists – who recover the exposed emerald crystals, which are then placed into lockable production boxes and taken to the sorting house. The balance of the material in the contact zone is loaded into ADTs and taken to the processing plant for recovery of emeralds – and beryl – not detected by the hand mining.” A strip-and-fill mining method is used by Kagem. This involves stripping the high wall and filling in the exhausted footwall with the hard rock, which contains the size of the pit and keeps the environmental liability under control. Stripping ratios are enormous com- pared to conventional mines and are currently varying between 80 and 100 to 1 as a result of increased contractor stripping. While the mining operation at Kagem is huge and quite complex, the processing operation – which is chemical-free – is very straightforward, involving ore crushing and washing followed by screening in a triple-deck unit, after which the material reports to a pick- ing belt facility where the emerald crystals are picked out by hand from a series of picking belts. The picking operation goes on around the clock in three eight-hour shifts, with lower quality material being processed at night. The final part of the process involves the cleaning

Chisel men at work watched by security personnel.

A Cat 336D excavator loads a Cat 730C ADT. Kagem’s mining fleet is modern and well maintained.

and grading of the emeralds in the sort house and their assembly into parcels for auction. Interestingly, the management at Kagem is mainly composed of Indian expatriates, headed by C V Suresh, who is Director of Operations. The total number of expats is currently 59 but,

Kagem carries the flag Kagem, which has three rivers (including the Kafue and the Kafubu) on its boundaries, is located in the central part of the Ndola Rural Emerald Restricted Area (NRERA). The discovery of beryl (emeralds are a gemstone variant of beryl) in the area dates back to 1928 although mining of emeralds on any significant scale apparently only began in the 1970s. The Kagem mine is one of only three sizeable mines in the area but the NRERA also hosts several hundred informal miners. Kagem is by far the big- gest producer and has been described by the Zambian government as “the flag-bearer company of the Zambian gemstone industry.” 

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April 2015  MODERN MINING  35