Mining and Exploration Methods
North West Province Project Area
Namakwa's mining activities in the North West Province are currently concentrated on producing mines in the Central Node, South Western Node, Southern Node and South Eastern Node and utilise conventional open pit mining and strip mining methods with slight variations on approach depending on the type of gravel being exploited at each site. The two most common diamondiferous gravels identified at these sites are the red unconsolidated Rooikopie gravel and the thicker, calcretised Vlei gravel. Mining of the unconsolidated Rooikoppie gravel is usually undertaken first, as this sits closer to the surface than Vlei gravel.
Rooikoppie gravel is in a non-cemented form of approximately 0,3m to 1m in thickness and is usually covered with less than a 1m thickness of overburden. It is excavated using strip mining techniques with a bucket excavator used to remove the overburden prior to mining, minimising extraction costs. The resultant gravel is then excavated using similar techniques and equipment and transported to nearby rotary pan plants for processing. There is no requirement to blast away the overburden or gravel and the overburden material and unused gravel is dumped back into the mined out pits as backfill for rehabilitation purposes.
In comparison, calcretised Vlei gravels are usually extremely hard and have to be drilled and blasted, utilising heavier machinery and at more expense. The cementing effect of the calcrete also requires a crushing circuit to be installed in the processing section to liberate any diamonds caught up in the resulting matrix. The overburden is relatively thin and is usually discarded. Namakwa is currently in the process of analysing whether the overburden for Vlei gravel on its sites in the North West Province is economically diamondiferous, and since the introduction of blasting techniques to the region in 2003, many old "mined out areas" and other open pits not previously rehabilitated, have been revisited by both mining companies, including Namakwa, and local diggers to exploit further gravel from these sites, in an economic manner.
