Industrial garnet as an unconventional heavy rare earth element resource: Preliminary insights from a literature survey of worldwide garnet trace element concentrations

Current global supply of the critically important Heavy Rare Earth Elements (HREE) may be insufficient to meet future demand unless new sources are identified. This study utilizes trace element data in the literature to evaluate the potential of garnet, a common industrial mineral, to be further developed as a HREE-enriched mineral resource. A compilation of garnet REE data (n > 1,900 individual garnet analyses) demonstrates that garnet in metapelitic host rocks can have higher concentrations of the HREE dysprosium (Dy) through lutetium (Lu) in comparison to many of the existing and prospective sources of the Rare Earth Elements (REE). Furthermore, consideration of a smaller dataset containing garnet REE in addition to uranium and thorium concentrations indicates that many of the garnets with elevated HREE content also have uranium and thorium concentrations below those of the prospective and existing sources. As a case study, data from an actively mined garnet placer in northern Idaho (Emerald Creek), indicates that its proven garnet reserve contains ∼ 12 Mt of Lu alone despite its relatively small size. In total, the data indicate that experiments focused on the economics of extracting REE from garnet are warranted.