monaziteNd

Monazite-(Nd) is a rare earth phosphate mineral of the monazite group in which neodymium (Nd) is the dominant rare-earth element. The ideal endmember has the formula NdPO4, but natural samples typically contain Nd together with other light rare earth elements such as Ce, La, Pr, and Sm, with thorium and uranium often present as trace substituents. In mineral nomenclature, this Nd-dominant variety is written monazite-(Nd). The mineral forms a solid solution series with other monazite endmembers.

Monazite-(Nd) is monoclinic and typically occurs as reddish-brown to yellow-brown prismatic crystals or grains. It has a Mohs hardness around 5 and a relatively high refractive index. It is commonly associated with minerals such as zircon, xenotime, apatite, and allanite, and it occurs in granitoid rocks, high-grade metamorphic rocks, pegmatites, and as detrital grains in heavy-mineral placers.

Geologic occurrence: Monazite-(Nd) forms during late-stage crystallization of granitic magmas, in high-temperature metamorphic environments, and in pegmatites. Detrital grains are a common component of beach and river placer sands, where weathering and transport concentrate heavy minerals including monazite.

Economic significance: Monazite-(Nd) contributes to the supply of neodymium and other light rare earth elements. Because monazite commonly contains thorium and sometimes uranium, its processing requires regulatory and environmental considerations to manage radioactive elements. Monazite is often mined or recovered with other REE-bearing minerals and refined to obtain individual elements such as Nd.

See also: Monazite, Monazite-(Ce), Neodymium.