Finsch has an age of 118 ± 2.8 Ma (Smith et al., 1985), and is a Group-2 kimberlite (Smith, 1983a; Fraser and Hawkesworth, 1992). The geology of Finsch Mine in the open-pit and on the 348 m underground sampling level was described by Clement (1982). The pipe was emplaced through a thick sequence of Proterozoic, Griqualand West sequence sedimentary rocks comprising dolomites, banded iron formation and shales. Preserved within the pipe are large fragments of Karoo-aged sediments, lavas and dolerite which were clearly present at the time of emplacement, but have been subsequently eroded away.

Clement defined eight kimberlite varieties in the mine which he called F1–F8. F1 was described as being the most significant volumetrically and was classified as a diatreme-facies TKB. This variety hosted numerous very large blocks of down rafted Karoo basalt lava and sedimentary rocks. The F5 variety was also described as TKB, but occurred within a satellite portion of the pipe called “the precursor”. The other varieties were classified as hypabyssal kimberlite or kimberlite breccia.

Exploration of deeper levels of the mine found that the F8 variety increased in size with depth, and that the lithiccontent of the F1 declined with depth. Mapping of deeper levels has also revealed the presence of steeply dipping bedding planes within both the F1 and F8 varieties. Ekkerd et al. suggested that the F1 and F8 could be the same kimberlite, varying only in lithic content and alteration.

Steady state production from Block 5 SLC to be reached in H2 FY 2020.

Block 5 SLC production commenced from first tunnels on 70L – FY 2016.

Production on 75L commenced in Q3 FY 2018; all tunnels in production in Q3 FY 2019.

Construction of ground handling infrastructure completed in Q1 FY 2019.

Block 5 SLC ramp up:
– FY 2017 – 0.8 Mt
– FY 2018 – 1.7 Mt
– FY 2019 – 2.5 Mt
– FY 2020 – 2.9 Mt EST
– H1 FY 2020 – 1.5 Mt
– H1 FY 2020 ROM grade of 57.4 cpht in line with guidance of 54 – 57 cpht.

The new plant includes the installation of high-pressure roller crushers to replace the relatively dated rod milling process used before, and two new secondary crushers, replacing the older technology cone crushers.

Density (Dense medium separation)
• Diamond - SG = 3.52
• Kimberlite - SG = 2.65

-Hydrophobic and oleophyllic (grease recovery)

-Colour (transparent – optical sorting) Shape (shape sorting)

-Non-magnetic (magnetic separation)

-Fluorescence (X-Ray recovery)