A Comprehensive Report on Rare Earth Elements in Wyoming - 2016

Rare Earth Deposits & Mining

Sutherland and Cola of the Wyoming Geological Survey reported in 2016 that the rare earth elements (REE) are a group of 17 metals with similar physical and chemical properties that include the lanthanide series elements plus scandium and yttrium. Sixteen REE occur in nature, while promethium (Pm) is highly-unstable and occurs in very, very small concentrations on Earth. REE are considered strategic metals in the United States and are necessary for energy generation, transportation, data transmission, and national defense. However, production of REE has been negligible in the United States since the early 2000s. Production increased briefly with the 2010 re-opening of Molycorp’s Mountain Pass Mine in California, but since the closure of this operation in 2015, there has been no domestic production.

Planned mining and processing of the Bear Lodge REE deposit by Rare Earth Element Resources, Ltd. in northeastern Wyoming held promise for significant new United States production until poor market conditions forced the company to temporarily halt operations in early 2016. A restart of that project could replace production formerly provided by Molycorp and reduce dependence on China, which has accounted for more than 90 percent of the global supply in the past decade. Exploration for REE that began several years ago, when prices were high, continues across the country, although at a reduced level due to current lowbREE prices.

In Wyoming, investigations in the mid-20th century identified many sites that either hosted REE or were later interpreted to be potential REE occurrences. Unfortunately, these studies lacked complete elemental analyses. In 2012–13, the Wyoming State Geological Survey (WSGS) collected samples from many known, suspected, and potential REE host rocks and analyzed them for REE content and other potential economic elements. That data was published in WSGS Report of Investigations 65 by Sutherland and others (2013). Many samples were collected and analyzed for RI-65, and the aim of the RI-71 study is not only to analyze additional sites but to provide further information on sites that showed higher REE concentrations in the 2012–13 investigation.

This report contains data from the 2015 field season and summarizes previous studies to produce a comprehensive report on the investigations of REE in Wyoming. REE enrichment occurs in a variety of geologic environments across Wyoming. These environments include carbonatites, granites, pegmatites, epidosite dikes, calc-silicate pods and dikes, iron-rich silicate pods, paleoplacers in marginal marine sandstones, phosphatic horizons in marine shales and lacustrine mudstones, and apparent secondary mineralization from fluid movement within porous sandstones. The WSGS has developed a publicly accessible online database, the Wyoming Database of Geology (WyoDOG), which contains locations, geologic settings, and analyses for all samples in this and earlier reports. This database may aid mineral exploration across the state by identifying REE and other potentially economic elements.