Lithium – Hard-Rock and Brine

By November 13, 2018Lithium

Capital is limited in the current mining exploration environment, so investors are increasingly looking for companies that have lower costs of doing business. Over the last four years, we’ve seen large-scale, low-grade projects go out of favour and investor preferences resting with low-CAPEX, high-return projects.

However, it is not only the construction costs and scale of a mine with which companies can save money. It can also be in initial prospecting, exploration, and the development of a project. The key here is for a company to be doing this work in a location setting that is easy to work in from logistical and cost perspectives. If a project is in a remote area in mountainous wilderness that requires setup of a camp and bush planes in and out, the payoff has to be that much higher.

This is where lithium brine deposits come in. Typically, they are located in salars (salt flats) which are flat, arid, and barren areas. This makes the logistics of setting up shop for exploration relatively straightforward, and also removes most topographical challenges of exploration.

Further, there are some other major benefits of lithium brine exploration from a cost perspective that makes it favourable to many hard rock projects. Lithium brine deposits are considered placer deposits and are easier to permit. Brine is also a liquid which means that drilling to find it is more akin to drilling for water, and once it is found the continuity is more straightforward. It’s also typically not located relatively close to surface, which limits the amount of meters drilled.

Once a deposit is discovered, advanced exploration and development can also be at a discount. Drilling wells and testing recovery are more like shallow oil wells or drilling for water. Finally, permitting for construction and production is faster because of the placer classification.

Lithium brine exploration has benefits from the angle of cost that make it less expensive than most comparable hard rock projects.

Lithium is present in a number of different minerals, but for those who deal with its commercial extraction, there are really only a few that are of interest.

Pegmatites

Pegmatites are commonly found throughout the world, but lithium-rich granite pegmatites are much less common, making up less than 1%. Granite pegmatite-ore bodies are the hard-rock source of lithium. The lithium minerals that occur in granite pegmatites are spodumene, apatite, lepidolite, tourmaline and amblygonite.

Spodumene is the most commonly occurring lithium hard-rock mineral, which, once upon a time, made it the number one source of lithium metal in the world. It has since been surpassed by brines, which, for a number of reasons, have become the largest contributor to lithium production.

Pegmatite Hard-Rock Processing

Lithium hard-rock recovery can be broken down into a few key steps: crushing of the ore, concentration by froth floatation, followed by hydrometallurgy and precipitation from an aqueous solution. From here, depending on the application, the producer will typically create either lithium hydroxide or lithium carbonate, which can be sent to factories to be manufactured into its final form.

When evaluating a hard-rock lithium deposit, there are a few key things to look for:
Lithium Grade – Arguably the most important figure in any type of deposit. Typically, the higher the grade of lithium, the more economic the deposit.

By-Products – Not to be confused with ‘harmful’ impurities, by-products can help reduce the cost per ton because they have value. For lithium hard-rock deposits, tantalum, beryllium and caesium are examples of profitable by-products of the refinement process.

Impurity Levels – High concentrations of impurities (non-profitable by-products) can lead to higher refinement costs and could limit their use in end use applications, such as glass and ceramics.

Location – Poor proximity to infrastructure can make a high grade lithium mine a lot less profitable or not even economically feasible.

Brines

Lithium brine deposits are accumulations of saline groundwater that are enriched in dissolved lithium. Lithium concentrations are typically measured in parts per million (ppm), milligrams per litre (mg/L) and weight percentage.

Brine is pumped up from the ground and placed into man-made ponds, where the lithium is concentrated via evaporation. Depending on the climate and weather in the region of the brine deposit, lithium concentration can take a few months to a year. Typically, lithium concentrations range between 1 and 2%. Unlike their hard-rock cousins, these concentrations can be sent to processing plants for end use production.

All lithium brine deposits have a few common characteristics (Bradley, Munk, Jochens, Hynek, Labay. USGS – A Preliminary Deposit Model for Lithium Brines, 4).

  • Arid climates
  • Closed basin containing a playa or salar
  • Tectonically driven subsidence
  • Associated igneous or geothermal activity
  • Suitable lithium source-rocks
  • One or more aquifers
  • Sufficient time to concentrate a brine

Similarly to the list of common characteristics for brine deposits, there are a few things that are particularly important when evaluating a brine deposit:

Evaporation Rate – evaporation is dependent upon the climate in which the deposit is located. Hours of sunlight, humidity, wind levels and temperature all have an effect on the evaporation rate. A low evaporation rate could make the difference between an economic deposit and an uneconomic one.

Lithium Grade – Arguably the most important figure in any type of deposit. Typically, the higher the grade of lithium, the more economic the deposit.

By-Products – Not to be confused with ‘harmful’ impurities, by-products can help reduce the cost per ton because they have value. For lithium deposits, the primary by-product is potassium.

Location – Poor proximity to infrastructure can make a high grade lithium mine a lot less profitable or not even economically feasible.

Impurity Levels – The magnesium to lithium ratio and the sulphate to lithium ratio are very important figures to look at when examining a brine deposit, because separating these impurities from the lithium is one of the largest expenses in the brine refinement process. For both of these ratios, you’re looking for low figures.

Brines are today’s answer to lithium demand as they are more wide spread, typically larger in resource scale, and generally have lower production costs. Countries such as Chile, Argentina and China extract the majority of their lithium production from brine deposits.

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