Enhancing Processing Strategies of Claystone Ores: Li-Bearing Smectites from Oregon, USA
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Authors
Fish, Andrew
Issue Date
2025
Type
Thesis
Language
en_US
Keywords
Clay , Lithium , Metallurgy , Mineral , Mining , Processing
Alternative Title
Abstract
The demand for lithium has dramatically increased in the last few decades, as the unique metal finds itself at the forefront of efforts to produce cleaner energy across the globe. Meeting the demand requires new sources of lithium, spurring an interest among the mineral processing community in Li-bearing sedimentary claystones, an ore type that has never been processed on a commercial scale, largely due to the notoriously difficult nature of processing clay minerals. However, both academic and industrial leaders alike have recently begun tackling this challenge, a collaborative effort that continues here. This study highlights lithium-bearing smectitic ores obtained from the McDermitt Caldera in southeastern Oregon, USA, that have never before been analyzed in a metallurgical setting. Eight total samples were studied, two of each from four ore categories: 1) high grade, 2) rich clay, 3) clay-carbonate, and 4) miscellaneous. A “scoping study” approach was adopted for the claystones, through which they were subjected to experiments across multiple stages of a conventional mineral processing flowsheet to inform future research on related materials. The Li-claystones were tested in four major stages: 1) characterization, 2) comminution, 3) beneficiation (via enhanced gravity concentration), and 4) extraction (via direct acidification). Characterization using x-ray diffraction (XRD) and inductively-coupled plasma, mass spectrometry (ICP-MS), revealed that the clay mineral phase in all samples was smectite with no observable illitic components, and major gangue minerals were calcite, alkali feldspars, quartz, and zeolites. Comminution through attrition scrubbing and rod milling were both used to grind the ores for separate tests in Falcon enhanced gravity concentration and direct acidification. Samples varied in recovery after beneficiation with the Falcon, with a maximum Li recovery achieving over 90%, while most samples fell in the range of 50 – 60%. Recoveries for attrition-milled samples were slightly higher than that of the rod-milled samples at averages of 62.6% and 55.2%, respectively. In direct acidification experiments, 2 M sulfuric acid was used to leach the claystones. Most samples saw > 99% Li extraction after just 30 minutes of leaching at 80 °C, and rod-milled samples consistently recovered lithium slightly faster than attrition samples, although they achieved similar recoveries. Results show that both attrition milling and rod milling are effective strategies for grinding the ore and that it is amenable to sulfuric acid leaching. Future studies are recommended to focus on optimization of enhanced gravity separation parameters.