The Lace Mine lies within the south central Archean Kaapvaal Craton within a subcluster of kimberlites referred to as the Kroonstad Group II Kimberlite Cluster (Howarth, 2010) of which only Lace and nearby Voorspoed have seen formal mining. Four other small kimberlite blows and several dykes are known within the cluster.

The Lace Mine lies within the south central Archean Kaapvaal Craton within a subcluster of kimberlites referred to as the Kroonstad Group II Kimberlite Cluster (Howarth, 2010) of which only Lace and nearby Voorspoed have seen formal mining. Four other small kimberlite blows and several dykes are known within the cluster.

Drilling from surface through the wallrocks into the kimberlites in 1997-98 outlined a relatively simple stratigraphy of Karoo shales to ~60m, Ventersdorp volcanics to ~300m, an intercalated shale/volcanic sequence to ~350m, clean lavas again to 380m, and then Kameeldoorns Formation shales again to ~550m, the deepest wall rock drilling to date, in hole Crown-1. We therefore do not believe that Transvaal Supergroup rocks are present at Lace based on drilling to date.

The Lace kimberlites have been dated at 133.2 +/- 2.8 Ma by the 40Ar/39Ar technique on ground mass phologopite grains, similar to the early Cretaceous ages of the other Kroonstad kimberlites and to other Group II kimberlites in South Africa including Finsch.

The report concluded that a continuous trough type doming mining method incorporating a sub level open stope mined from the bottom, best suits mining of the UK4 block. The greatest risk of mining any block close to old workings is the potential risk of inundation of water and mud from the old workings. The chosen mining method – called Longhole Open Stoping Bottom Up (LOSBU) - meets the requirements of the SIMRAC report on the guidelines to mitigate potential risk of mud rushes.

The LDM UK4 Upper Lift 1 block design layout comprises two main levels, namely a doming level (290m level) and the main production level (310m level) as shown schematically in Figure 3. Two open stopes are positioned to extract the required ore tonnage from the block. Two continuous troughs will be situated for ore collection below the Open stopes. The doming level will be situated on 290m level to enable doming long hole rings to blast ore down into the collection troughs. This ore will be loaded from draw points spaced along the troughs. One stope will be mined initially and once this has broken through to the old workings and the mud and water is dissipated and drawn down the second stope will be mined. Lift 2 on the 360m level will be similar, with the ultimate layout slightly larger.

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