Hardrock and Brine Sources of Lithium

Although lithium is found in trace amounts in various mediums around the globe, the main sources of lithium for commercial extraction are localized hardrock pegmatites (igneous rocks of post magmatic fluids) and continental brines (saltwater aquifers). Other sources of lithium, including geothermal brines, oilfield brines and hectorite clays are also being evaluated for future exploitation.

Mineral Sources

Lithium-containing ores, which are primarily found in pegmatite formations, are widely distributed, with deposits found on every continent of the globe. Of the various ores found in pegmatite, spodumene ore is generally the most economically viable source of lithium. 

The spodumene mine in Greenbushes, Western Australia is the largest active lithium mine in the world. The ore mined from this facility exhibits the highest concentration of lithium oxide (Li2O) available. The second largest source of spodumene is found in Pilbara, Western Australia. Kings Mountain, North Carolina hosts the third large spodumene resource. 

A number of startups have begun mining spodumene in Mt. Cattlin and Mt. Marion, Western Australia and in Quebec, Canada. There are also considerable exploration efforts underway in the Pilgangoora, Wodgina and Goldfields regions of Western Australia. Additional pegmatite resources are found in China, Russia, Brazil, India, Mozambique, Zaire, Republic of Congo and Zimbabwe.

Mineral Extraction and Processing 

Pegmatite is extracted from open pit systems using traditional mining techniques. The extracted “lumps” of pegmatite are then mechanically crushed to reduce their size. The crushed ore is further milled to produce a finer product, which is more suitable for further separation in floating cells. In these cells, the various other minerals, including quartz, feldspar and micas, are removed. This results in the formation of a spodumene concentrate which can be either sold for direct application in the manufacture of glass and ceramics or chemically processed to create lithium carbonate or lithium hydroxide. 

Although there are a number of processes for derivatizing spodumene concentrate, they all begin with lithium extraction from ore followed by chemical conversion and then purification.

Brine Sources

Over the past 40 years, brines have become a viable alternative to spodumene mining. Brines, which are salty, mineral-rich solutions occurring in aquifers, are typically found in arid regions with specific geological conditions. Many of these briny aquifers were created by volcanic and geothermal events or through the eventual percolation of runoff containing high concentrations of ash. These events facilitate the leaching of minerals from the surrounding rock, particularly lithium chloride. 

The first large-scale extraction of lithium brine occurred in Clayton Valley (Silver Peak, Nevada) in 1966. Lithium-rich brines are also found throughout South America, in the Central Andes region. However, these brine deposits, referred to as “salars,” vary substantially in terms of lithium concentrations and mineral compositions (i.e., lithium-magnesium ratios), and are exposed to different weather conditions (i.e., evaporation rates, precipitation rates, wind patterns and ambient temperatures), all of which influence the ability to economically recover lithium from each salar. 

Currently, the Salar de Atacama in Northern Chile and the Salars del Hombre Muerto and de Olaroz in Northwestern Argentina are the only actively producing salars on a commercial scale. Of these, the Salar de Atacama exhibits the highest lithium concentration and the most favorable extraction conditions of any brine resource in the world. 

There are many other sources of brine being evaluated by various companies focused on lithium extraction, including the Salar de Antofalla and the Salar del Rincon in Argentina, the Salar de Maricunga in Chile, the Salar de Uyuni in Bolivia, the Qaidam Basin in China, and Zhabuye Lake in Tibet. Geothermal brines (e.g., the Californian Salton Sea deposit) as well as oil-field brines are also under investigation.

Brine Extraction and Processing 

Brine containing high concentrations of lithium is pulled from saltwater aquifers using extraction wells. From the wellhead, the brine is diverted to an evaporation pond system. Using solar evaporation, the lithium salts are concentrated in the brine and eventually routed to the next pond in the system. This step is continued multiple times, until the lithium concentration reaches a level high enough for conversion to lithium carbonate or lithium hydroxide. 

The altitude and inherently arid conditions of the regions where these brine resources are found contribute to an evaporation process that is completely powered by the sun. Solar evaporation has been praised as being environmentally responsible because it does not rely on the use of fossil fuels to concentrate the brine. Other minerals and impurities are also precipitated during the evaporation process, requiring little-to-no chemicals. The entire concentration process can take 12 to 18 months. 

During evaporation, other minerals, which typically contain sodium, potassium and magnesium, precipitate from the brine, leaving higher concentrations of lithium chloride (LiCl). The resulting concentrated LiCl brine from the terminal pond of the system is then routed to a processing plant where it is converted to lithium carbonate, lithium hydroxide or lithium chloride. 

There are other means of lithium extraction from brines using adsorbents or chemical extraction, but these processes have yet to be proven on a commercial scale.

Last Updated: 12/13/2016 12:46:52 PM