Underground mine to extract beauvoir granite
In the 1980s, the French Geological Survey (Bureau de Recherches Géologiques et Minières, BRGM) conducted a nationwide search for metal alloys for the aerospace industry. At Échassières, a 900-meter-deep borehole revealed rock particularly rich in lithium, with a lithium oxide content of 0.9% (Li2O): this rock is Beauvoir granite, which Imerys proposes to mine underground.
In addition to its lithium concentration, Beauvoir granite has the advantage of being easy to access (the deposit containing the lithium is located at a shallow depth and its lateral extension is reduced to the existing site footprint). In addition, the underground mine would preserve the landscape and minimize the environmental impact of the project.
Mining of the deposit would begin at its lowest point at a depth of around 400 meters and continue upwards, in stages, to 75 meters below the surface.
The granite would be extracted by opening galleries and excavating chambers measuring 25 meters high and across. Up to eight chambers would be mined simultaneously before being backfilled with non-recyclable materials. The granite would be crushed underground before being brought to the surface.
What is lithium content?
The lithium content of a mine refers to the concentration of lithium in the ore extracted. It is a key factor in assessing the potential profitability of a lithium mine and its environmental impact. The higher the lithium content, the greater the concentration of lithium in the ore. The lithium content of the Beauvoir deposit is around 0.9% Li2O, while many other deposits in Europe are around 0.6%. Today, elsewhere in the world, some projects are being undertaken with a much lower content, of the order of 0.2%, meaning that much more energy has to be expended and more ore extracted to obtain the same quantities of lithium.
