Lithium (Li) is a soft, silver-white alkali metal fundamental to modern energy technology. It is the lightest of all metals and is highly valued for its ability to store large amounts of energy within a small mass. Its primary application is in lithium-ion batteries, which power electric vehicles and nearly all portable electronic devices, such as smartphones and laptops. The escalating worldwide demand for high-capacity energy storage has made the search for new, economically viable lithium deposits a global priority, requiring a detailed understanding of the geological environments where it concentrates.
Primary Geological Settings for Lithium
Lithium is highly reactive and is not found in its pure metallic form, but occurs within compounds concentrated across three distinct geological settings. The most common source currently is lithium-rich brine, a highly saline fluid found beneath salt flats, or salars, primarily in arid, high-altitude regions. These deposits form when water leaches lithium from surrounding rocks, flows into closed basins, and evaporates, concentrating the lithium salts in the subsurface brines. The “Lithium Triangle” of Chile, Argentina, and Bolivia hosts the largest known reserves of these brine deposits.
The second major source is hard rock deposits, where lithium is bound within crystalline minerals inside igneous formations called pegmatites. Pegmatites are coarse-grained rocks that form when magma cools slowly deep within the Earth’s crust, concentrating lithium-bearing minerals. The most significant lithium mineral found in these deposits is spodumene, an aluminosilicate mineral that requires conventional surface or underground mining techniques. Australia is a leading producer of lithium from these hard rock sources.
An emerging source is sedimentary clay deposits, which contain lithium-rich clay minerals like hectorite. These deposits form when volcanic ash or lithium-bearing rocks weather, trapping the resulting lithium ions within lacustrine sediments in closed basins. Locations like Nevada in the Western United States are known for these clay-based resources. Extracting lithium from these clays presents unique challenges compared to brines and hard rock, often requiring specialized chemical processing methods.
Exploration and Survey Techniques
The process of finding new lithium deposits begins with remote sensing, where geologists use satellite imagery and aerial surveys to identify areas with favorable geological characteristics. Spectral analysis of the ground surface can reveal evaporite minerals or surface alteration patterns associated with subsurface brine or clay deposits. This initial, broad-scale assessment helps narrow vast geographic areas down to smaller, more promising targets for fieldwork.
Once a target area is identified, exploration shifts to geochemical sampling to look for anomalous concentrations of lithium. In brine environments, this involves analyzing surface and subsurface water samples to determine lithium grade and the presence of impurities like magnesium. For hard rock and clay deposits, geologists take rock chip, soil, and stream sediment samples to test for elevated lithium levels. Drilling boreholes is then undertaken to extract rock cores or fluid samples for precise laboratory analysis of the deposit’s grade, thickness, and structure.
Geophysical surveys provide a non-invasive way to map the geological structures that might host lithium beneath the surface. Techniques like gravity surveys measure density variations, which help delineate deep basin structures containing lithium-rich brines or locate dense pegmatite bodies. Electromagnetic (EM) and magnetotelluric (MT) surveys are particularly useful in brine exploration because they measure the electrical conductivity of the ground. Since lithium brines are highly conductive, these methods map the extent and thickness of the saturated, lithium-bearing layers underground.
Extraction Methods Post-Discovery
After a commercially viable deposit is proven, the raw material must be processed into a usable lithium compound, typically lithium carbonate or lithium hydroxide. For brine deposits, the traditional method involves pumping the lithium-rich liquid from underground reservoirs into vast, shallow evaporation ponds. The sun and wind slowly evaporate the water, a process that can last from months to over a year, progressively concentrating the lithium salts. As the brine concentrates, unwanted salts precipitate out. The remaining liquid is then chemically treated with agents like sodium carbonate (soda ash) to precipitate the final lithium carbonate product.
Hard rock extraction from spodumene-bearing pegmatites requires a different, more energy-intensive industrial process. First, the ore is mined using conventional techniques and transported to a processing facility where it is crushed and ground into a fine powder. The lithium-bearing minerals are separated from the waste rock through flotation, a technique using chemicals to selectively float the desired minerals. The resulting spodumene concentrate is then subjected to high-temperature roasting, often exceeding 1,000 degrees Celsius, followed by chemical leaching to dissolve the lithium and produce a pure lithium compound.
Newer technologies, such as Direct Lithium Extraction (DLE), are being developed and implemented to target lithium from brines more efficiently. DLE technologies utilize advanced processes like ion exchange, solvent extraction, or adsorption to selectively remove lithium from the brine. This approach significantly reduces the need for large evaporation ponds and can drastically shorten the processing time from years to hours or days. These innovative methods aim to decrease the environmental footprint and accelerate the conversion of raw resource into battery-grade material.