It appears to be regular dirt, rock and gravel, but this material has a value beyond its looks. The largest, single known source of bauxite is to be found just below the topsoil on the west coast of Africa.
Roger Thea, Factory Director at the CBG plant in Kamsar.
The stockpiled bauxite is conveyed into the plant for crushing and drying.
It is high noon at the CBG (Compagnie des Bauxites de Guinée) open pit mines in Sangaredi, and the temperature has already reached a scorching 35°C. We are about 11 degrees north of the equator in Guinea on the west coast of Africa. In the comfort of his cabin five metres up, Balla Patrice Guilavogui is giving us a broad, white smile. He is proudly riding his massive 102-tonne Komatsu wheel loader at the CBG mines, moving bauxite gravel and rocks which could in essence be considered metal in disguise.
Mr Guilavogui in his loader is at the very start of the fascinating trail leading to the shining commodity we know as aluminium.
It is here in the rolling hills of Sangaredi, just below the thin topsoil, that we find the largest and richest bauxite deposit in the world. It is a rust-coloured layer with a moderate thickness of about eight metres, but of huge proportions stretching inland far beyond the hazy horizon. The mines here have to date delivered more than 260 million tonnes of bauxite to the world market, amounting in modest terms to about 70 million tonnes of pure aluminium metal.
Our guide, Geology Supervisor Kaba Camara, explains: “The bauxite here is a hard, rocky layer which has to be loosened. We blast on average every second day so the drilling going on here now is for the blasting tomorrow. You should have been around to see and photograph it. It is quite spectacular.”
Of the several opencast mining facilities found in western and central Guinea, Sangaredi is by far the largest, with an average daily output of about 39,000 tonnes. The bulk of the ore here is also considered high grade with over 50% Al2O3, mainly as gibbsite, which is a trihydrate oxide in the bauxite mineral family.
“However,” Kaba Camara remarks, “this means that our bauxite has substantial amounts of unwanted water trapped in the oxide. Therefore a processing plant for the run-of-mine ore is situated near the harbour in Kamsar for crushing and drying the bauxite before shipment. And the ore is transported 134 km from here to there by a quite remarkable train configuration.”
And indeed it is. 1.5 km long trains with more than one hundred ore-filled wagons leave Sangaredi 5–6 times a day.
A tandem three-engine-system pulls this load of nearly 10,000 tonnes of ore across the plains from the mine to Kamsar at the coast.
“Loading the train is done by wheel loaders which move temporary stockpiles at the mine into the wagons, but emptying them here has a twist to it,” says Factory Director Roger Thea at the CBG plant in Kamsar. “We simply turn them over.”
An ingenious contraption lifts each of the heavy wagons to a height of about four storeys and turns them over so they release their contents into a funnel in three-minute cycles. From here, the bauxite is transported by different conveyor belts to stockpiles around the factory.
The bauxite is crushed and heated to 600–700°C in three rotating ovens – reducing the water content from 12.5% to 6.7% – and then stored in covered stockpiles. When the ship at port is ready, the processed bauxite is sent via the conveyor belt on the 1.6 km jetty to the shiploaders.
In Kamsar we are also welcomed by Captain Mamadou Alpha Diallo of Afrimarine s.a., a ship agency responsible for marine surveys and customs clearance at the port.
He enthusiastically explains that “the port here is a busy one, handling around 230 shipments a year. It can handle vessels loading up to about 60,000 dwt, and it is tidal, so ships have to leave at high tide. The cargo quantity therefore varies with the magnitude of the tide.”
From here, about 13 million tonnes of bauxite find their way around the globe each year – to be refined into alumina and metallic aluminium – and finally to be used to make a multitude of aluminium products. The process has just begun.
Text and photos: Per Sverre Wold-Hansen
Date: 05 February 2008