JOHANNESBURG (miningweekly.com) – Southern African diamond development and exploration company DiamondCorp has finalised the £23-million finance package for the 47-level block cave development at its Lace mine, in the Free State.

The company reported on Wednesday that it had received the final funding tranche of £1.96-million from Laurelton Diamonds, a wholly owned subsidiary of Tiffany & Co, on schedule. The combination of funding through the £3.91-million Tiffany loan, £4.2-million of convertible bonds and £15.6-million from the Industrial Development Corporation completed the £23-million Lace project financing package.

The main pipe at the Lace mine, in which DiamondCorp held a 74% interest, contained 33.1-million tons of kimberlite with an indicated and inferred resource to a depth of 855 m containing about 13.4-million carats at an average grade of 40.1 carats per hundred tons. At a carat value of $160/ct, the resource had an in-ground value in excess of $2.1-billion.

The deposit is to be mined using the block-cave method, with three caves planned over the next 25 years on the 47, 67 and 85 levels at depths of 470 m, 670 m and 850 m, respectively. The kimberlite was open at depth, and also contained a significant bulge between 250 m and 360 m at depth with the potential to add additional tonnage and diamonds.

In February, DiamondCorp started the excavation of a new 66 000 bank cubic metre (BCM) boxcut, which would provide the surface entrance to the twin conveyor belt and services declines for the life of the mine. A total of 23 000 BCM of surface sediments and clay material was excavated by the end of March and the boxcut was expected to be completed on schedule in the current quarter.

Underground blasting was started in March with a vent raise on the 16 level to provide sufficient interim ventilation for continuous blasting of the twin decline development to the 47 level. DiamondCorp indicated that the raise development was continuing on schedule and was expected be completed in the current quarter.

Development on a tipping arrangement on the 24 level to allow loading of development waste into dump trucks for hauling to surface until such time as the conveyor belts were installed, was also under way.

Between February and March, the company completed the rebuild of a 9.5 t underground loader and two underground dump trucks in its on-site heavy equipment workshop. Two additional low-profile loaders and three additional underground dump trucks were bought in February, completing the fleet requirements for the underground development.

These units would be rebuilt and commissioned during the next two quarters, in line with the planned development programme.

Meanwhile, essential upgrades were under way on the mine's 1.2-million-ton-a-year dense media separation plant to allow smooth transition from tailings to kimberlite processing and relieve front-end bottlenecks in the re-crush circuit. These modifications were on schedule and plant recommissioning was planned during the current quarter, allowing tailings retreatment activities to restart.

DiamondCorp had prepared a drilling cubby on the 26 level inside the main pipe and had ordered a new skid-mounted underground drilling rig, which is being shipped from Australia and was expected to be delivered and commissioned during the next quarter.

A total of 2 km of underground drilling was then planned in the bulge area, as well as the 47 level block cave area, to better define the kimberlite margins and facies distribution.

“We are pleased with the progress achieved with the operations in the first quarter and remain on target to start diamond production from tailings retreatment in the next three months.

“This will initially be on a one-shift basis, while the upgraded processing plant is recommissioned. We will then have the capacity to ramp up to three shifts in the second half of the year depending on diamond prices,” CEO Paul Loudon said in a statement to shareholders.