Lithium Production: Pegmatite vs. Brine

Lithium brine and pegmatite is the lightest of all metals and is used in several industrial, technological and medical applications. The market is currently interested in lithium, its compounds, and specifically, its use as a component in lithium batteries for electric vehicles (EV’s). The market for lithium supplies is precipitously rising due to the current growth demand for EV’s. Currently, Lithium makes up 3% of the total cost of a Lithium ion battery, which is comparable to the standard for batteries in EV’s due to the battery’s similar format of storage cells. . EVs use over 5000 times more lithium in their batteries than a cell phone, which is where the demand is continuously and exponentially growing.

Lithium, a finite element constituting about 0.006% of the earth’s crust, has been mined and used in batteries and other items since the early twentieth century. A reactive alkaline metal, lithium can be found in lithium salts and minerals. Since World War One, lithium has been used in alkaline storage batteries. But it’s use expanded after World War Two, where it was predominantly used in greases, ceramics, glass, and air-conditioning, as well as alkaline dry cell batteries. The historical use of lithium suggests that its current demand is not a new phenomenon resulting from the recent technological boom, making cell-phones, computers, lap-tops, and electric vehicles every day items.

Today, we can find lithium in two primary sources: lithium bearing salts in brines and hard rock pegmatites containing lithium-bearing minerals.

Lithium Demand and UBS forecast

Hard Rock Lithium Deposits

In Canada, the predominant deposit type for lithium is hard rock LTC (lithium, tantalum, cesium) bearing pegmatites which are found in the Canadian Shield of NE Canada. Almost all lithium pegmatites are intrusives for metamorphic rocks. The primary lithium-bearing minerals in pegmatites are spodumene, amblygonite, petalite, and or lepidolite. Pegmatites are generally coarse-grained rocks composed of additional minerals, including feldspars, quartz and micas. There typically is zonation of the minerals in the pegmatites with variation in lithium content including contact zones with no lithium-bearing minerals.  Lithium exploration and development in Canada largely focuses on finding Spodumene, a mineral containing the highest amount of lithium. Spodumene is a lithium aluminosilicate that has a maximum Li2O mass content of 8.03%. It’s Li20 mass content typically ranges from 4.5% to 7.5%; anything higher than 7.5% is rare. The amount of spodumene in an average pegmatite could be up to 30%. Meaning, pegmatite’s overall grade can range from 1.7% Li2O to 2.0%, but the average spodumene rich pegmatite is closer to 1.7%. This gives the range for a “high grade” spodumene lithium bearing pegmatite. Historically only pegmatites that could be hand sorted for spodumene crystals greater than one foot in length were mined. Current technologies allow for mining and sorting by mechanical means.

The development of lithium from hard rock deposits is the predominant method currently underway in Canada through the discovery of spodumene-bearing pegmatites of economic size. Nemaska’s Whabouchi project and North American Lithium’s Lacorne project both exploit surface deposits of spodumene-bearing pegmatites.

Nemaska Lithium, Spodumene pegmatite exposed for mapping and sampling

Defining a resource on a pegmatite dyke can take a significant amount of work. In order to prove a pegmatite exists, a company has to first locate the intrusive body and then conduct surface work on it, including mapping, sampling and drilling to define the size, dimension and the overall grade of the pegmatite deposit. Pegmatites can be dykes or sills of varying orientations and sizes. For example, the Lacorne deposit in Quebec is a pegmatite dyke swarm extending over 1km. Whereas, Far Resources deposit is a part of a dyke swarm with several other identified dykes on the property extending over 300m.

The next step in the development of a hard rock resource is the collection of a larger tonnage representative bulk sample to determine lithium recoveries to a concentrate, its grade and content of any deleterious elements such as iron. This work is typically conducted at a third-party testing facility. Basic mineral processing equipment is used to make a concentrate. The deposit is mined from an open pit using standard drilling, blasting, and excavating techniques. It’s then delivered to the processing plant where it is crushed and ground down to the desired particle size, where the lithium-bearing spodumene is separated from the rest of the pegmatite minerals, including quartz, feldspars and micas.  Separating the spodumene from the other minerals occurs by dense media separation and/or flotation, distinguishing the spodumene through its chemical composition and mass. As in the case of Nemaska, the average grade of the deposit is 1.57% Li2O in spodumene and the concentrate grade is approximately 6% Li2O, equating to a concentration ratio of roughly 4:1.

This spodumene concentrate forms the basic production material for battery grade lithium chemicals. Lithium chemicals are produced by further processing the spodumene concentrate. From here, it is determined if the lithium chemicals meet the specification for the battery-grade material. Lithium carbonate and lithium hydroxide are the two main lithium chemicals. Battery grades for these chemicals are generally greater than 99.5% purity, while four 9s commands a premium product. Companies who are developing a spodumene pegmatite need to determine if an economical concentrate can be made from the deposit. Next, they need to determine if the concentrate can be further processed into battery grade lithium chemicals.  

Chemical Plant Process Flowsheet

A company has two choices when it comes to the production of the spodumene concentrate: either the concentrate, itself, is the final product, or they can use a chemical plant to further produce the concentrate to make lithium chemicals for batteries or other industrial applications. Both Nemaska and North American Lithium projects selected the latter option, using chemical plants to further process the spodumene concentrate.

 

The process for development of the lithium project then is the same as any other mining operation. The project requires both economic and environmental studies showing the viability and potential of financing and development. In order to secure funding, companies can either establish partnerships with the companies involved in the chemical production of lithium through joint ventures, or they can create an off-take agreement securing the supply to their battery factories. The process from drilling to feasibility took Nemaska seven years. Full production is at least 18 months from completion.

Lithium Brine Deposits

Lithium brine deposits occur in closed basins with high evaporation rates that lead to the formation of salt lakes or salars. The lithium is derived from the decomposition of the rocks in the basin, which collect as a part of the brine in the lower part of the basin. The brine is full of highly saline fluids that collected in the sediments of the closed basin. The salt flat is the surface expression of the brine deposit collected. There are no salt lake lithium brine deposits in Canada. However, there are lithium-bearing brines occurring in formations which have been intersected by oil drilling in western Canada. Groups are examining different methods to try and recover lithium from these formational brines. These brines can be accessed from existing oil wells. Lithium brine production can occur through salars. All salars contain lithium-bearing brines. Approximately 50% of lithium chemicals are currently produced from brines. The major operations using this type of lithium production are located in the high Andes of South America. The process of developing a salar lithium resource starts with securing a land package in the salar basin. These basins are known and ownership is generally fragmented. Once a claim for the basin has been made or a group is obtained, you need to determine the quantity and quality of the existing brine. This can be done through drilling and sampling.

The salar basins consist of a mixture of clays, silts, sands and evaporites that are saturated with saline brines. These saline brines contain dissolved lithium minerals and other dissolved solids which need to be removed for purification. The salts precipitate in solar ponds where evaporation causes a concentration of the salts that are removed in a sequence. These salts are removed as a by-product or a cost of removal. Through evaporation, the lithium concentration in the remaining brine increases until it precipitates as lithium carbonate [with the addition of soda ash]. Evaporation may only be effective for part of the year. There are design criteria for a sequence of evaporation ponds to limit losses. The design must be monitored for evaporation rates, leakage, flow rates, depths of the ponds and input concentrations in order to ensure the final solution contains the high-grade lithium brine.

Lithium Brine Deposits

To determine the quantity and quality of the salar brine deposit, a drilling program is required to establish the location and characteristics of the deposit. The lithium-bearing brine may only occur in a certain stratigraphic section or unit of the basin, which is why drilling is required. Exploration wells in the salar basin may be several hundreds of feet deep.  They are typically of large diameter in order to enable pumping tests to determine the flow parameters of the reservoir.  

 

Brine lithium concentrations are generally lower than spodumene deposits. At Clayton Valley, NV the brines grade 0.04% lithium or 400 ppm. A salar in Argentina, under option to Ultra Lithium, is reported to grade an average of 227 ppm lithium.  The end product of the salar project is a lithium carbonate that can be sold directly to battery makers. However, since every salar brine is different, it requires a specific design to remove the unwanted additional elements, such as magnesium, from the brine and the final product.

 

Additionally, in order to determine if the lithium brine project is viable, the projects need to determine the recovery and cost parameters and include it in their budget. The project cost and chemical characteristics can be determined by sampling the brines through pump tests and laboratory recovery testing. Sample lithium chemical products can be produced for testing by end users as well for off take considerations. A production project requires a series of large diameter wells for brine collection, a series of evaporation ponds and a purification and treatment plant. Final products can be transported by truck or rail to ports or end users.

Lithium brine projects also need to determine recovery and cost parameters to input into economic studies to determine if the project is viable. The project cost and chemical characteristics can be determined from sampling of the brines through pump tests and laboratory recovery testing. Sample lithium chemical products can be produced for testing by end users as well for off take considerations. A production project requires a series of large diameter wells for brine collection, a series of evaporation ponds and a purification and treatment plant. Final products can be transported by truck or rail to ports or end users.

There is the potential for the direct production of lithium chemicals from certain brines using solvent extraction technology without the use of evaporation ponds. The lithium is recovered to lithium chloride, where the remaining brine is returned to the basin. This method is at the pilot plant stage at a project in Nevada.

Comparison of Methods:

Hard Rock

Strengths

  • Higher lithium grades
  • Standard mining methods
  • Standard recovery methods
  • Intermediate concentrate is saleable product
  • Production starts with plant completion

Weakness

  • Significant drilling and sampling to define
  • High energy costs of mining, milling, transport
  • Time to complete studies
  • Time to construct large milling plants
  • Requires additional processing to chemicals
  • High capex for mining and mill equipment
  • Needs good infrastructure for development

Salar Brines

Strengths

  • Low operating costs
  • Low capex costs
  • Can expand production more readily
  • Makes end product Lithium carbonate.
  • Needs only road and limited power
  • Can operate at lower grades

Weakness

  • Water resource depletion
  • Land subsidence
  • Salt needs to be sold, disposal costs
  • Poor recoveries generally < 50%
  • Product requires time in ponds to collect
  • Requires costly soda ash to make product
  • Fragmented claim ownership in salars
  • Often located in less secure jurisdictions
  • Evaporation may be seasonal