The Rincon lithium project is a high-grade lithium project in the Salar del Rincon, Argentina. Credit: Argos Minerals.
The lithium project is expected to start commercial operations in mid-2022. Credit: Argos Minerals.
The project’s pilot plant was commissioned in April 2018. Credit: Argos Minerals.

The Rincon lithium project is located in the Salar del Rincon salt pan in Argentina. Australian firm Argosy Minerals owns 77.5% interest in the Puna Mining joint venture (JV) that owns 100% interest in the project.

Pablo Alurralde and Francisco Menendez are the JV partners in the project. Argosy holds the right to increase its stake in the JV to 90% in return for investment in stage three of the project development.

A preliminary economic assessment (PEA) for the project was completed in November 2018. An initial modular plant will have a production rate of 2,000t per annum (tpa) of lithium carbonate (Li₂CO₃). It is expected to be operated for two years. The company plans to expand the Li₂CO₃ production capacity to 10,000tpa in the subsequent years.

An environmental impact assessment (EIA) was submitted for the 10,000tpa expansion in July 2021, with final approval expected by the end of 2021.

Rincon lithium project development details

The project is being developed in multiple stages. Stage one comprised a pilot plant that was commissioned in April 2018 and produced the first batch of lithium carbonate in June 2018. Continuous pilot plant trial runs commenced in June 2019.

Stage two involves the development of a 2,000tpa operation, which is currently under construction with completion expected by April 2022. The plant commissioning works, production test-works, and production ramp-up will take place upon the completion of construction. Commercial production of battery-grade Li₂CO₃ is expected to start in mid-2022.

Stage three development of the project will depend on the success of stage two.

Rincon lithium mine location and geology

The Rincon lithium project is located at the Salar del Rincon in the Salta province of Argentina. The project encompasses up to 2,794ha of mining titles and landholdings. It is a part of several highly mineralised salt flats currently in production and development in the arid Puna region.

The sedimentation within the salar comprises halite, sand and clay formed due to the terrestrial sedimentation and evaporation of brines. The flat-lying units feature semi-confined aquifers near the surface and confined conditions at depth. The mineralised brines within the salar saturate the entire sedimentary sequence from 1m below the ground level.

Mineralisation and reserves

An extensively fractured halite aquifer extends over the surface of the salt flat with an average thickness of 11m. Sandy aquifers with an average cumulative thickness of 50m occur within the underlying mix of sand and clay in the deposit.

The lithium brine project was estimated to contain an indicated mineral resource of approximately 245,120t of Li₂CO₃ with lithium grading at 325mg per litre, as per November 2018 estimates.

Lithium processing at Rincon lithium project

The Rincon lithium project will utilise standard lithium extraction techniques and solar evaporation. The brine from the aquifers will be pumped from production wells to a series of solar evaporation ponds in the pond facility.

The salt will be precipitated, which will trap a portion of the lithium in the brine. Lime will be added to assist in the precipitation and reduce the quantity of magnesium, sulphate, and boron in the brine. The Li₂CO₃ plant is expected to produce Li₂CO₃ at a purity grade of 99.5% or higher.

The saturated lithium brine from the evaporation ponds will be processed to remove magnesium, boron, and calcium before being forwarded to the carbonation stage. Lime will be added to remove magnesium, while soda ash will be added to precipitate the residual calcium in the brine as calcium carbonate. The residual sulphate from the brine will be precipitated with the addition of barium chloride.

Solvent extraction method will be used to remove boron resulting in an almost boron-free brine, which will be pumped to the carbonation stage. Temperature control and carbonation with soda ash and carbon dioxide gas will precipitate Li₂CO₃ from the brine solution to produce lithium bicarbonate. Lithium carbonate will go through the second phase of precipitation to remove the majority of the contaminants.

The precipitated Li₂CO₃ will be thickened and filtered to produce a dewatered Li₂CO₃ filter cake, which will be dried and milled for packaging.

Off-take agreements

Argosy Minerals executed a sales agreement with Mitsubishi Corporation Rtm Japan for an initial supply of up to 100t of battery-grade Li₂CO₃ for 12 months in March 2019.

The two companies signed a non-binding head of agreement (HOA) for the supply of 2,000tpa of Li₂CO₃ for three years in August 2019. The agreement also includes an extension option of two years. The first shipment under the agreement was made in May 2020.

Contractors involved

The PEA for the project was prepared by the engineering firm Primero Group. Water resources consultancy AQ2 and price reporting agency Benchmark Mineral Intelligence also provided services in support of the PEA.