Bastnäsite is the world’s most economically important rare-earth-element (REE) mineral, a fluorocarbonate of cerium, lanthanum and neodymium. The Bayan Obo deposit in Inner Mongolia is the single largest REE resource on Earth, supplying roughly 40-60% of global light-REE production for decades.
Properties
- Formula: (Ce,La,Nd)CO3F
- Crystal system: Hexagonal
- Hardness: 4 – 4.5
- Color: Honey-yellow to reddish-brown, tan, brown
- Streak: White to pale brown
- Luster: Vitreous to greasy
- Cleavage: Imperfect on {1010}
- Density: 4.9 – 5.2 g/cm³
Occurrence in China
Bastnäsite’s headline locality is Bayan Obo, Inner Mongolia, where it is intergrown with monazite and magnetite in carbonatite-related Fe-REE-Nb ore. Maoniuping in Sichuan is the second-tier Chinese producer and yields the finest collector specimens — bright honey-yellow crystals on aegirine and barite matrix. Globally also at Mountain Pass (California) and Karonge (Burundi).
Identification
Honey color + hexagonal habit + association with carbonatite host (aegirine, barite, fluorite) is diagnostic. Bastnäsite is mildly radioactive due to thorium substitution and fluoresces a soft cream-orange under SW UV in some Maoniuping material.
Collector Notes
Maoniuping crystals on aegirine matrix are the gold standard for the species. Pair with monazite, xenotime and fluorite for a complete REE display.
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)
