Wagner (1914) described two main kimberlite varieties, as well as examples of late-stage internal dykes. Clement (1982) recognized three varieties of kimberlite in the main pipe, which he named KOF1-3. These comprised two diatreme-facies (KOF1 and 2) and a hypabyssalfacies kimberlite (KOF3). The KOF-1 variety was a TKB that occupied the main pipe, whereas KOF-2 was a TKB that occupied the “West Fissure”. The KOF-3 variety was the hypabyssal intrusion that occurred as the “East Fissure”. A further notable feature was the presence of a large floating reef comprising various Karoo lithologies in the main pipe. A satellite kimberlite pipe named Ebenhaezer, which also contained diatreme-facies kimberlite, is located close to the main pipe. Clement speculated that these two pipes once coalesced to form a single large crater.

Mapping of deeper levels by Naidoo et al. (2004) found evidence for at least two main volcaniclastic kimberlite varieties in the main pipe, and demonstrated that these were geochemically distinct based on their groundmass spinel compositions. They described the layered nature of the “floating reef” as well as intermixing between layered breccias and relatively lithic-poor volcaniclastic kimberlite. They also demonstrated that the kimberlite between the floating reef and the eastern contact at depth to be geochemically distinct from the main kimberlite variety that had been mined throughout the life of the mine. They called into question the appropriateness of the “TKB” classification of Clement (1982).

Production commenced from 56 Level SLC – FY 2015.

Ground handling system commissioned – Q3 FY 2018.

Production from 60L commenced – Q2 FY 2019.

SLC Production Ramp Up:
– FY 2017 – 0.6 M
– FY 2018 – 0.7 Mt
– FY 2019 – 1.0 Mt
– FY 2020 – 1.0 Mt EST
– H1 FY 2020 – 0.56 Mt
– H1 FY 2020 ROM grade of 7.9 cpht marginally below guidance of 8.0 – 8.5 cpht.

Once a diamond operation yields ore, the diamonds must be sorted from the other materials. Excavated ore is transported to a processing plant.

The kimberlite is first crushed and then processed through the plant, which consists of a series of screens, jigs and scrubbers and a gravity pan or DMS plant to remove lighter particles and create a concentrate of heavy material, which includes the diamonds.

Diamonds are then extracted from this material by using an X-ray machine and/or grease table and checked by hand sorting. Most diamonds luminesce under X-rays and can therefore be identified and separated in final recovery. However, some diamonds – particularly more valuable Type II stones – do not respond well to X-rays, so grease tables are used to recover such stones. As diamonds are hydrophobic (meaning they repel water), they stick to the grease while the rest of the wet concentrate runs off.

The treatment of ROM kimberlite ore produces a sink (high den ........