01 March 2023
American Battery Technology Company (ABTC) (earlier post) announced results of its third-party Qualified Person (QP)-audited Inferred Resource Report that details the analysis of its lithium deposit at its Tonopah Flats Lithium Project in Nevada. The inferred resources report concludes that Tonopah Flats may hold an estimated 15.8 million tons of lithium carbonate equivalent.
Inferred mineral resource is that part of a mineral resource for which quantity and grade or quality are estimated on the basis of limited geological evidence and sampling. The level of geological uncertainty associated with an inferred mineral resource is too high to apply relevant technical and economic factors likely to influence the prospects of economic extraction in a manner useful for evaluation of economic viability.
Because an inferred mineral resource has the lowest level of geological confidence of all mineral resources, which prevents the application of the modifying factors in a manner useful for evaluation of economic viability, an inferred mineral resource may not be considered when assessing the economic viability of a mining project, and may not be converted to a mineral reserve.
Resource estimates were calculated based on a pit-constraint, conservative cutoff concentration of 300 ppm Li that support a 200,000 ton per day claystone process rate. There is potential to expand the resources significantly with further drilling extending to the north and south property boundaries and at greater depths.
The lithium mineralization at Tonopah Flats occurs predominantly in the claystones of the Siebert Formation. The identified claystone thickness in the project area exceeds 800 feet. The overall sedimentary package within the project area is flat lying to gently dipping. Fine laminations and “waxy” textured clay seen in the drill cuttings are thought to be correlative with higher lithium grades.
The lithium-rich sedimentary claystone resource has demonstrated to be amenable to a selective leaching process, enabling economically viable lithium recovery.
The ABTC Tonopah Flats Lithium Project encompasses 517 unpatented lode claims covering approximately 10,340 acres that is administered by the Bureau of Land Management (BLM). ABTC began geologic exploration on the project area in 2021, and the results of this successful exploration program led to the publication of the Inferred Resource report.
ABTC controls 100% of the mining lode claims comprising the Tonopah Flats property and the rights to all locatable subsurface minerals without any royalties. ABTC began surface sampling of these claims in the Summer of 2021, and subsequently performed multiple subsurface drilling programs totaling 12,000 feet of exploration covering approximately 65% of its property.
In order to perform an unbiased analysis of this data, the mineral resource estimates presented in the ABTC Tonopah Flats Inferred Resource Report were performed by third-party qualified person (QP) RESPEC, LLC, and were classified by geological and quantitative confidence in accordance with the Securities and Exchange Commission (SEC) Regulation S-K 1300. Through this analysis an open-pit resource estimate was developed that would support a processing rate of at least 200,000 tons of claystone per day.
The lithium resources at Tonopah Flats were modeled and estimated by:
- Developing a geological model of the deposit
- Evaluating the drill-hole lithium assay data statistically
- Utilizing the geological model as the base for interpreting lithium mineral domains on a set of cross sections spaced at 500-foot intervals
- Projecting the sectional mineral-domain polygons horizontally to the drill data within each sectional window, thereby creating three-dimensional polygons
- Using the polygons to create three-dimensional wireframe solids of the mineral domains
- Coding a block model comprising 100 x 100 x 20 (x, y, z) -foot blocks to the mineral domains using the wireframe mineral-domain solids
- Analyzing the modeled mineralization domains statistically to aid in the establishment of estimation and classification parameters
- Interpolating lithium grades by inverse-distance to the third power into the block model using the coded lithium-domain percentages to explicitly constrain the grade estimations
- Constraining the resource with a pit optimization to determine a shape and cutoff grade satisfactory to meet the requirement of reasonable prospects for eventual economic extraction
Status of exploration, development, and operations. Exploration conducted by ABTC commenced in the Summer of 2021 and has included both surface sampling and drilling. ABTC collected 29 surface samples in June 2021 to confirm elevated lithium values from samples collected by a previous owner. The surface samples returned an average of 314 ppm lithium with a maximum of 882 ppm lithium.
ABTC commenced drilling at the Tonopah Flats property in December of 2021. A total of 12,000 feet were drilled in 10 reverse circulation holes and 12 air core holes during two phases of drilling prior to October of 2022. Drill holes were spaced approximately 200 ft to 3,500 feet apart. All holes were drilled vertically and ranged from 400 to 885 feet in depth. Lithium mineralization was encountered in all 21 drill holes submitted for analysis.
Metallurgical testing and mineral processing. The Tonopah Flats lithium-rich sedimentary claystone readily disaggregates when suspended in water. Standard assaying of head grades was performed using a representative array of samples selected from 21 drill holes. For metallurgical leaching trials, bulk samples from the Tonopah Flats project were prepared for lithium leach trials using roughly 700 pounds of cuttings from the 2021-2022 drill hole program.
These metallurgical leaching trial samples were collected from drill hole TF-2208, where the average head-grade for lithium was found to be about 790 ppm. The sample was homogenized by cone-and-quarter methods and pulverized to 100 mesh to obtain a statistically repetitive sample.
Mineral processing was carried out at the University of Nevada, Reno’s Ore Dressing Laboratory. The claystone is responsive to dilute acid leaching as well as several methods of selective lithium leaching.
Leaching trials were carried out in-house by ABTC using statistically representative homogenized bulk samples, and these trials demonstrated that more than 90% of lithium can be leached from the claystone within a few hours. Following leaching, treatment of the pregnant leaching solution by pH adjustment/neutralization, filtration, solution purification, concentration, conversion, and final solution polishing/crystallization, battery-grade lithium hydroxide monohydrate can be realized.
To validate and optimize these metallurgical and mineral processing techniques further, ABTC summarized the results of its bench scale trials for the manufacturing of battery-grade lithium hydroxide specifically from these Nevada-based claystone materials in a $4.5-million proposal to the US Department of Energy (DOE), Advanced Manufacturing Office (AMO).
In this application, the ABTC team and its partner, DuPont Water Solutions, described its integrated mineral processing train in detail and proposed a plan for evolving these bench scale trials to a multi-ton per day continuous integrated field pilot plant to demonstrate the performance and economics of the overall system. In January 2021, ABTC was notified that the US DOE AMO had selected its proposal for funding and the projected initiated in October 2021.
Substantial trials, validations, and optimizations of these mineral processing unit operations have been performed to date within this government-supported project.
Due to the positive results from these bench scale validations, the ABTC team applied for a second round of US DOE funding in the Spring of 2022 to evolve this project and to construct a commercial-scale lithium hydroxide refinery utilizing this system design and the bench and pilot scale results from the initial program. In October 2022, ABTC with its partners, DuPont Water Solutions, University of Nevada, Reno, and Argonne National Laboratory, was notified that its proposal for its $115-million commercial scale refinery project was selected for funding. ABTC is now in the process of detailed construction design for this commercial scale lithium hydroxide refinery based on these fundamental metallurgical and mineral processing techniques.
Next steps. With the data generated in this report, ABTC intends to take the following steps to further advance this project:
- Perform a Preliminary Economic Assessment (PEA) to analyze the potential viability of this resource and the related commercial scale lithium hydroxide facility
- Perform additional infill and extension drilling to further expand the mineral resource to the North, South, and at depth and to advance the resource from Inferred to Measured and Indicated
- Publish an updated mineral resource report based on the additional drill data and continued metallurgical test work
- Evaluate the performance of the field pilot plant that is being constructed as part of the current US DOE Advanced Manufacturing Office grant in order to further detail the economic viability of the lithium hydroxide refinery
- Perform a Pre-Feasibility Study (PFS) to quantify the impacts of developing this resource and constructing the commercial scale lithium hydroxide refinery