 Described by the United States Geological Survey as one of the greatest deposits of rare-earth minerals in the world, the pegmatite was the first place geologists discovered fergusonite, monofergusonite, thorogummite, yttrialite, and nivenite.The pegmatite is centrally located in the Lone Grove pluton, a 1.6 Ga old rapakavi granite, intruded into Valley Spring Gneiss.Geologic evidence suggests the pluton's emplacement as a rather shallow intrusion of magma, possibly in a sub-caldera type situation.