Monazite is a light-REE phosphate and one of the two principal sources of cerium-group rare earths (alongside bastnäsite). It is mildly radioactive and serves as a key target mineral for U-Th-Pb geochronology.
Properties
- Formula: (Ce,La,Nd,Th)PO4
- Crystal system: Monoclinic
- Hardness: 5 – 5.5
- Color: Yellow-brown, reddish-brown, dark brown
- Streak: White to pale yellow
- Luster: Resinous to vitreous
- Cleavage: Distinct on {001}
- Density: 4.9 – 5.5 g/cm³
Occurrence in China
Monazite occurs at Bayan Obo (Inner Mongolia) intergrown with bastnäsite, and at Maoniuping (Sichuan) as carbonatite-hosted crystals. Coastal placer deposits in Guangdong and Hainan historically supplied monazite-rich heavy mineral sand. Globally also at Madagascar, Brazil and India.
Identification
Yellow-brown wedge-shaped monoclinic crystals, high density (~5 g/cm³), and weak radioactivity distinguish monazite from xenotime (tetragonal, lower density) and zircon (tetragonal, much harder).
Collector Notes
Madagascar produces the largest gemmy monazite crystals, but Maoniuping yields jewel-like stubby crystals on matrix. Often paired with bastnäsite and aegirine in displays.
Found at these Localities
- Maoniuping REE Mine (牦牛坪稀土矿)
- Bayan Obo Mine (白云鄂博)
- Inner Mongolia (内蒙古)
- Sichuan (四川)
- Maharashtra Deccan Traprock Zeolites (马哈拉施特拉德干玄武岩沸石产地)
- Eastern Brazilian Pegmatite Province (巴西东部伟晶岩省)
