Re-established after the re-discovery of immense mineral deposits in the last century, Phalaborwa supports a vast mining industry, including one of the world's largest open-cast mines supplying vital minerals to the country. It is here that most of South Africa's copper is mined, in an unique fashion- the open pit is 450 m deep, measuring nearly 2 km in diameter and, as the world's deepest open-cast mine with the tallest headgear, has become a unique tourist attraction.
The mine museum is located in the first house built in Phalaborwa. There is also a viewpoint over the Big Hole, once a notable saddle-backed hill called Loolekop. Famous geologist Hans Merensky in 1938 found valuable minerals in this kop and it has been totally mined away. The mine is currently undergoing a unique transition from wholly open-cast to an exclusively underground operation.
Mine Geology - overview
The profusion of minerals in the area is attributed to a series of volcanic eruptions 2,000 million years ago. The Phalaborwa area also boasts the only Antimony mine in the Southern Hemisphere at nearby Gravelotte. The cone of the eruption has vanished, but the pipe, an astonishing geological feature, remains. The pipe is 19 square kilometres in area and is filled to an unknown depth with minerals such as phosphates, copper zirconium, vermiculite, mica and gold. A history of mining through the ages at Phalaborwa is here.
The current open-pit copper mining scheme commenced at Phalaborwa in 1964. Current integrated copper metal refining capacity is 135,000 tonnes per year, and the mine is also a major source of vermiculite and baddeleyite (zirconium oxide). However, open-pit mining ceased in May 2002 and is being replaced by an underground operation with a further 20-year life. Development investment in the underground mine is some $410 million. The operation employs around 2,400 people.
The Phalaborwa mine contains magnetite, vermiculite, apatite, zirconium, titanium and uranium as well as copper. The deposit is hosted in an alkaline igneous complex comprising mainly pyroxenite with occurrences of pegmatites, foskorite and carbonatite. Three separate mineralised zones have been identified within the complex’s 20km² surface outcrop, of which the most northerly is phosphate-rich while the central (Loolekop) zone forms the basis for Phalaborwa’s copper production. Detailled geology of the mine is here.
At the end of 2001, proven reserves were 3.3 million tonnes of 0.85% grade copper in the open pit and 225 million tonnes of 0.7% copper in the underground section of the orebody. Probable underground reserves were 16 million tonnes of 0.49% copper.
|Ore milled (Mt)||28.3||25.7||14.5|
|Copper head grade (%)||0.47||0.59||0.66|
|Copper concentrates produced (kt)||333.4||358.7||233.5|
|Contained copper (kt)||111.9||117.0||78.4|
|Refined copper produced (kt)||100.1||87.7||86.9|
|Uranium concentrates (t)||91.0||95.0||31.0|
|Zirconia products (kt)||11.1||7.9||4.0|
Production Statistics for the last Three Years
Throughout its 35-year life, Phalaborwa has often been at the forefront of surface mining technology developments. A key feature has been its use of a trolley-assist system for haul trucks coming out of the pit, and it was one of the early users of both in-pit crushing and computerised truck despatching. However, the pit's last blast took place on 25 April 2002.
The underground mine is a block caving operation, the first such system to be used in metal mining in South Africa. Ore output will fall from the previous 82,000 tonnes per day to 30,000. Mining is under way but final development of the undercut and drawpoints is scheduled for November 2004.
The Big Hole is so large that it is visible from space
Shaft Sinkers was contracted to install the main service shaft and 1,280m-deep production shaft, while RUC Mining Contracting has been carrying out the underground development. This included driving around 36km of tunnels plus the underground crusher stations, ore handling infrastructure and the undercut level for the first block cave, situated 500m below the final pit bottom. The crushing stations are being fitted with four ThyssenKrupp 900t/h double-toggle jaw crushers that feed a 1.32km conveyor linking to the production shaft.
Phalaborwa employs one of the most complex recovery circuits installed at any copper mine, producing eight metal, mineral and chemical products in around 20 different varieties and grades. The complex includes a concentrator, copper smelter and refinery, currently capable of producing 135,000t/y of copper plus by-products. Phosphate-rich tailings are delivered to Foskor, while Phalaborwa sells its own copper, precious metals, nickel, zirconium, magnetite and vermiculite on domestic and world markets.