お知らせ • Sep 22
Ioneer Ltd. Announces Potential for Increased Organic Growth at Rhyolite Ridge
Ioneer Ltd. announced test results revealing 79% of the 360 million tonne Mineral Resource can be processed in a similar manner to Type 1 mineralisation, to create critical electric vehicle battery materials within the Rhyolite Ridge Project’s existing footprint. Previous estimates indicated Rhyolite Ridge contains enough lithium to power more than 50 million electric vehicles over the course of its lifetime; results support those figures. The potential to increase the lithium and boron produced and refined at Rhyolite Ridge comes at a time when the demand for a U.S. domestic supply of lithium continues to grow. According to a recent S&P Global study, the passage of the Inflation Reduction Act (IRA), caused a 15% increase to their 2035 demand forecast versus their estimate prior to the passage of the IRA. Once operational, Rhyolite Ridge will quadruple the current U.S. supply of lithium and help to rebalance the global production of boric acid. Upon anticipated completion of the U.S. federal permitting process, Stage 1 construction at Rhyolite Ridge, largely funded through the combination of conditional commitments of $490 million USD in equity from Sibanye-Stillwater and $700 million USD in debt from the U.S. Department of Energy’s Loan Programs Office, is set to begin in 2024. Lithium production is expected to follow in 2026. With a total of more than 400 individual leach tests across the entire 360Mt Mineral Resource, the latest results showed the low-boron, low-clay mineralisation (Type 3) shares similar characteristics to the high-boron Type 1 mineralisation, with leach recoveries between 89%-94%. The findings build upon the April 2023 Mineral Resource Estimate (MRE) and together, provide an update to Ioneer’s 2020 Definitive Feasibility Study (DFS)3, which focused exclusively on the high-boron, low-clay mineralisation (Type 1). The metallurgical testing on the low-boron, low-clay material (Type 3) was undertaken to determine the most efficient and economic processing pathway for this material. Lithium extraction measured between 89-94% using sulfuric acid under heap and vat leaching conditions applied to coarsely crushed material (P80, <19mm). These extractions, coupled with the free draining nature of the material suggest that Type 3 mineralisation is a candidate for heap or vat leaching methods industrially, similar to those employed for the high-boron Type 1 mineralisation. In these latest results, Ioneer has completed a metallurgical test work program comprising 120 separate leach tests exclusively targeting the low-boron Type 2 and Type 3 mineralisation. In addition, preliminary leach tests have been conducted on lithium mineralisation from the North Basin. Three distinct styles of lithium mineralisation, recognised in the April 2023 Mineral Resource Estimate, comprise: Type 1 Mineralisation: Lithium with high boron and low clay content (searlesite dominant, mainly illite clay) 152Mt Mineral Resource containing 1.2Mt of lithium carbonate equivalent (LCE). Type 2 Mineralisation: Lithium with high clay content (dominantly smectite clay) 75Mt Mineral Resource containing 1.0Mt of LCE. Type 3 Mineralisation: Lithium with low boron and low clay content (feldspar dominant, mainly illite clay) 128Mt Mineral Resource containing 1.1Mt of LCE. Mineralisation at Rhyolite Ridge: In April 2023, Ioneer published an updated Rhyolite Ridge Mineral Resource Estimate1 (MRE) that included all lithium mineralisation irrespective of its boron content. Previous MREs only included lithium mineralisation with >5000 parts per million (ppm) boron. Recent test work showed that a classification of the MRE based on clay content and clay mineralogy is highly relevant, in addition to the classification based on boron content. Clay abundance and clay mineralogy, above all other factors, determines the way the mineralisation can be leached (vat, heap, or agitated tank). Leach Testwork: Metallurgical testwork conducted by Kappes, Cassiday & Associates (Reno, NV) and Kemetco Research Inc. (Richmond, BC) has demonstrated that simple acid leach processes (vat and heap) can be used to extract lithium at high recovery from low-boron, low-clay mineralisation (Type 3) found in both the South Basin (S5 and L6 units) and the North Basin at Rhyolite Ridge. Testwork was conducted on drill core samples collected from six drill holes within the South Basin Mineral Resource area and two drill holes from the North Basin. Individual stratigraphic units were sampled across their entire thickness and samples were kept separate for each drill hole. The samples are considered to be representative of the low-boron, low-clay (Type 3) mineralisation found in the S5 and L6 stratigraphic units across the Mineral Resource. The samples were leached using leach parameters developed by ioneer from the >300 tests previously performed on the Type-1 mineralisation. Prior to leaching, the samples were crushed (P80 <19mm), homogenised and split into 4 equal parts. Samples of 2-3kg were used for each leach test. In additional to recording high leach recoveries, the samples remained free draining throughout the duration of the tests. These leach characteristics are only possible due to the low clay content of the mineralisation. In contrast, samples with high clay content from the M5 unit (Type 2) were deemed unsuitable for vat and heap leach testwork and instead were subject to agitation tank leach. The attraction of vat and heap leach methods over agitation tank leach is both a reduction in processing cost, water requirements and energy consumption together with dewatering and storage advantages for the leached ore. Vat and heap leach require only coarse crushing (P80 <19mm) and are free draining (no filtration required) during and after the leach process, meaning they are easier to wash, dewater, transport and store. This results in higher recoveries and negates the need for a tailings dam. Vat Leaching: A vat leach unit operation will be utilised for the high-boron, low-clay (Type 1) ore. A vat leach is a sulfuric acid flooded tank leach. The leaching solution is fed, bottom to top, through a series of seven tanks counter current to the ore loading. In lab test work, this operation is simulated by an ore column; where the leaching solution is fed from the bottom of the column, flooded up through the column, then collected from the top and recirculated, in a closed circuit, back through the column. Heap Leaching: Sulfuric acid heap leaching is typically used in the mining industry for low-grade ores. The crushed ore is configured into a large mound or heap on a lined leach pad. A leaching solution is then sprayed or dripped onto the top of the heap, percolating through and is collected from the base as a pregnant leach solution (PLS). The heap leaching operation is simulated, in the lab, by an ore column where the leach solution is applied to the top of the column and collected at the bottom.
