Southern Coastal Mine (SCM) is situated within Mining Licence No. 43 on the south-western coast of Namibia. SCM stretches from the Orange River at Oranjemund to Chameis Bay, about 100km north of Oranjemund. Raised Pleistocene diamondiferous beaches, ranging from 25m below mean sea level to +30m above mean sea level are responsible for the lion share of the carats produced by Namdeb and its predecessors since operations began early in the previous century.

The mineralised marine gravels have been washed onto shore from approximately two million years ago in the form of linear beaches driven by the southern winds and long shore drift. The diamonds were transported from the kimberlite pipes of southern Africa, along the mighty Orange River to the Atlantic Ocean. The large diamonds are concentrated in the south and as the gravel load moved along the coast the vigorous and persistent wave action sorted the diamond population into smaller stones and higher grades towards the Affenrucken area, some 80km to the north. This wave action and sand interacting with the bedrock structure caused gullies and potholes to upgrade the trapping of the diamonds. The diamonds and gravels were covered by marine and windblown sand varying between 25m in depth in the south to less than 6m in depth at Affenrucken. Geologists sampled this deposit using trenches spaced between 500m and 1km apart, evaluating the potential diamond content.

Ore is currently mined from an area within 15km from the southern limit of the mining licence. Stripping the overburden is done primarily with a dredger and a fleet of articulated dump trucks (ADT’s). The dredge pumps the fluidised overburden onto the beach and this plays a vital role in the building out of the shoreline (accretion) and the maintenance of the seawalls. The ADT’s remove the overburden and build seawalls to protect the mining operations from the onslaught of the Atlantic Ocean.

Younger foreshore terrace gravels that occur at current sea level are stockpiled for later treatment. These gravels are of low grade and currently two wet in-field screening plants are utilised to screen the oversize and fines material, upgrading the gravel which is then taken to the treatment plant. These screening plants are used to reduce haulage costs and are deployed far from the main treatment plant to maximise the savings effect on load and haul costs.

The high grade basal gravel is usually well entrapped in the bedrock depressions and is mostly less than a metre thick. Geologists pass areas as depleted and surveyors ensure that the advance lines are surveyed and captured on a geographical information system (GIS). The GIS is used in displaying data like monthly depletions, sample data, infrastructure and licence areas.
 

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