An Investigation of Rare Earth Element Occurrence at the Kennecott Copper Operation and Implications for Recovery

The seventeen elements that comprise Rare Earth Elements (REEs) are considered critical minerals by the United States Geological Survey (USGS). REEs have unique spectroscopic and magnetic properties that enable them to play an important role in industrial and advanced material sciences applications. However, the United States is nearly 100% reliant on imports for REEs, lacking sufficient domestic resources and processing capabilities. To ensure resilience across U.S. energy and defense needs, the United States must secure reliable and sustainable domestic supplies of REEs. To address this need, Rio Tinto has established a project to determine the ability and extent to which its North American Copper assets could provide REEs for the national supply chain. This project has focused primarily on Rio Tinto Kennecott, an integrated copper mining operation located in Utah. This project aims to characterize the enrichment of REEs and occurrence of REE-bearing minerals within the orebody and various processing streams at Kennecott and explore possible routes for their recovery. Here, we present characterization work completed thus far, including an evaluation of REE enrichment in the rock types present at the Kennecott mine, as well as results from a detailed mineralogical study of REE-enriched ore from Kennecott using bulk geochemistry, electron microscopy, and automated mineralogy. We also discuss the current outlook and options for recovery of REE-minerals given the occurrence of REEs within the Kennecott orebody and processing streams.