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Spodumene

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Spodumene is a pyroxene mineral with a chemical formula of LiAl(SiO3)2. It is a lithium aluminium inosilicate, which means it is a complex structure of lithium, aluminum, silicon, and oxygen. This mineral is a vital commercial resource because it is a primary source of lithium. Lithium is a key ingredient in many modern technologies. It is used to manufacture batteries for mobile phones and electric vehicles. It also has uses in medicine, ceramics, and as a fluxing agent.

Inside the mineral, the lithium is held very tightly within its crystal structure. This makes extracting the lithium a difficult industrial process. One common method involves roasting the ore at extremely high temperatures. When the temperature rises above 900 °C, a transformation occurs. The mineral changes from its low-temperature form, called α-spodumene, into a high-temperature form called β-spodumene. The α-spodumene belongs to the monoclinic crystal system. In contrast, the β-spodumene crystallizes in the tetragonal system. This new β-structure is more open and reactive, making it easier to process.

Once the mineral is in its reactive state, engineers use chemical processes to recover the lithium. Traditional refining often uses acid leaching to dissolve the lithium from the ore. This is followed by the precipitation of impurities and the concentration of the lithium solution. Finally, the solution is converted into lithium carbonate or lithium hydroxide. Another method is pyrometallurgical processing, which relies on the high-heat roasting mentioned earlier. Some modern methods aim to use noncaustic reagents. This can create a closed-loop process that produces less acidic or alkaline waste.

Tesla has developed a new way to refine lithium from spodumene concentrate. This process does not require the use of strong acids. Instead, it mixes sodium chloride, water, and the open-beta-structure concentrate together. High temperatures and agitation create a slurry that is rich in lithium. This slurry can then be filtered and purified into lithium hydroxide. This method may also reduce waste. The leftover sands and limestone can be repurposed as construction materials. A large $375 million refinery for this process is under construction in Robstown, Texas.

Spodumene has a long history of scientific study. The Brazilian naturalist Jose Bonifacio de Andrada e Silva first described the mineral in 1800. He found it at its type locality in Utö, Södermanland, Sweden. The name "spodumene" comes from the Greek word *spodumenos*, meaning "burnt to ashes." This name refers to the opaque, ash-grey appearance of the material after it is refined for industry.

This mineral is found in lithium-rich granite pegmatites and aplites across the globe. Major deposits exist in the Democratic Republic of Congo, Australia, Brazil, and Canada. In 2021, AVZ Minerals was developing a massive project in the Manono region of the DRC. This deposit has an estimated resource size of 400 million tonnes of high-grade ore. Australia has become a leading lithium producer, especially through the Greenbushes pegmatite in Western Australia. The Talison Minerals mine at Greenbushes is the world's second-largest mine. It holds a high ore grade of 2.4% Li2O.

Spodumene also produces beautiful gemstones through its different colored varieties. Kunzite is a purple variety caused by trace amounts of manganese. It was named after the mineralogist George Frederick Kunz in 1902. Hiddenite is a pale, emerald-green variety colored by chromium. It was named in honor of the mining engineer William Earl Hidden. There is also a yellowish variety known as triphane. These stones are valued for their strong pleochroism, which is a change in color when viewed from different angles.

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