Aquarius Platinum’s Blue Ridge project is situated on the Blaauwbank farm, about 30km south-east of Groblersdal, on the eastern limb of the Bushveld Igneous Complex (BIC), South Africa. The project was originally owned by Ridge Mining, which Aquarius acquired in July 2009.
Ridge Mining started exploration work on the project in 2001 and completed a feasibility study at the end of 2005. Mine development, estimated to cost $170m, began in January 2007.
The project is a 50:50 joint venture between Aquarius and BEE partner Imbani, which had invested more than $100m of equity by December 2008.
In December 2007, project finance agreements were signed with a consortium of banks consisting of the Development Bank of Southern Africa, the Industrial Development Corporation of South Africa, Standard Bank and Investec Bank for R715m, giving full finance through to first production which began in the first quarter of 2009.
The cash operating cost assumption for Blue Ridge is $660/oz to produce platinum, palladium, rhodium and gold, giving an expected payback period of five years. The first concentrate from the mine was shipped in April 2009.
In September 2010, it was decided to redevelop the mine and install infrastructure because of sub-optimal mine design and low rand basket prices prevailing at that time. The redevelopment project began in the last quarter of 2010.
During the redevelopment, the company concluded that the mine will not produce sufficient margins to justify further development spendings. It was found out that at the existing low rand PGM (platinum group metals) prices and the rate of mine cost inflation in the country, the mine cannot operate economically. As a result, the company froze mining operations and further development in the second quarter of 2011. Operations are expected to remain suspended until the rand PGM basket price improves.
The eastern limb of the BIC, like the rest of the complex, consists of distinct rock strata, including three PGE-bearing layers known as reefs, with one being the UG2 chromitite reef.
The PGEs in the UG2 chromitite occur primarily in discrete mineral phases, varying from sulphide assemblages (predominantly cooperite, braggite, malanite and laurite) to those consisting of a significant component of alloys (such as Pt-Fe alloy) or various telluride, bismuthinide, bismuthotelluride, arsenide and sulpharsenide phases.
Total Measured, Indicated and Inferred resources are put at 81.85Mt, giving a contained 4PGE figure of 8.38Moz at an average grade of 3.19g/t. Total proved and probable reserves are nearly 25.08Mt to give a contained 4PGE figure of nearly 2.42Moz at 3g/t.
The mine development is based on the central, north and truck ramp shafts. During 2008 work focused on opening up production levels and faces in readiness for mining to begin in earnest. The plan was to mine only the higher grade portion of the reef, using a method called "Efficient Cut".
Before the plant was commissioned, Ridge Mining stockpiled more than 200,000t of ore – about two months’ worth of throughput for the plant in full production – allowing enough ore to be processed through the concentrator plant while the underground workings continue the ramp-up to full capacity.
Annually the mine was forecast to produce about 75,000oz of platinum, 35,000oz of palladium, 22,000oz of ruthenium, 13,000oz of rhodium, 2,500oz of iridium and 1,500oz of gold over its initial 18-year life.
The ore is processed using crushing, milling and flotation, then milling and flotation again to produce a concentrate. The ore is fed through a primary ball mill and into primary roughers and cleaners, from where some of the feed goes to a care thickener and the rest to a secondary ball mill and roughers and cleaners, then on to tails thickeners. The concentrator plant is next to the entrance to the main decline shaft, which has a conveyor belt to bring the ore to the surface. Processing testwork show recoveries into concentrate of 82%-86%.
Aquarius had planned to boost its performance by re-treating the tailings and processing ore from Millennium, which was acquired by Ridge Mining from Lonmin in March 2008 for an undisclosed amount. Millennium has raised the original resources at Blue Ridge by more than 70% and allowed the company to mine at a higher rate because it gives a greater strike length. An offtake agreement was signed with Impala Refining Services for all the production from the mine.
Water comes from a combination of boreholes and the nearby Loskop Dam.
For electrical power, Ridge Mining signed up with state utility Eskom before the moratorium on new supply contracts. The first power line, which supplies about 70% of the mine’s requirements of 17MVA at full production, was installed in November 2008, with the rest installed in 2009. To cater for any shortfall in the interim and for any unforeseen outages, however, there are back-up diesel generators that can provide all the mine’s power, albeit at higher cost.
The process plant, which is operated by Minopex, was built by Bateman Engineering; Murray & Roberts Cementation are responsible for the underground mine development.