21 different veins, the ratio of rare-earth elements (REEs) in the area is estimated to be between 0.05-9.2%. This depends largely on the localized mineralogy and REE mineralization. Most commonly the thorium is found as thorite hosted in quartz veins, whereas REEs are contained within monazite. The deposits lie within quartz veins hosted in Precambrian rock with minerals such as hematite, apatite, feldspar, thorite and monazite present. The monazite is found to be enriched in the middle rare earths, specifically neodymium (Nd), as there is estimated to be 35 weight percent of Nd in the monazite. Neodymium, cerium, gadolinium, yttrium, and dysprosium are the top lanthanide minerals recorded to be attainable in the Lemhi Pass. See also Mountain passes in Montana List of National Historic Landmarks in Idaho List of National Historic Landmarks in Montana National Register of Historic Places listings in Lemhi County, Idaho National Register of Historic Places listings in Beaverhead County, Montana References External links National Park Service - Lemhi Pass Reading 2: Lemhi Pass and Lolo Trail from The Lewis & Clark Expedition: Documenting the Uncharted Northwest Name, a National Park Service Teaching with Historic Places (TwHP) lesson plan. Mountain passes of Idaho Mountain passes of Montana National Historic Landmarks in Idaho National Historic Landmarks in Montana Great Divide of North America Landforms of Lemhi County, Idaho Landforms of Beaverhead County, Montana Borders of Idaho Borders of Montana Transportation in Lemhi County, Idaho Transportation in Beaverhead County, Montana Beaverhead-Deerlodge National Forest Salmon-Challis National Forest Natural features on the National Register of Historic Places in Montana National Register of Historic Places in Lemhi County, Idaho National Register of Historic Places in Beaverhead County, Montana Lewis and Clark Expedition