Hexagonal
A U.S. Geological Survey review describes bastnäsite as the most important rare-earth-element (REE) mineral because it is the principal ore mineral in major carbonatite REE deposits; it is 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.
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.