BASTNÄSITE (from the name of the Bastnäs deposit within Sweden * EN: bastnäsite, bastnaesite; DE: Bastnasit; FR: bastnesite; ES: bastnaesita; RU: бастнезит) is the mineral, the fluoro-carbonate of cerium, Ce[CO3](F,OH). The composition (%) is: 73.5 of TR2O3; 8.5 of F; 19.8 of CO2. The impurities are: lanthanum and cerium lanthanides, yttrium and yttrium lanthanides, H2O. It crystallizes into the hexagonal crystal system. The structure is sub-layered. The crystals are prismatic, more often granular aggregates. The colour is yellow, reddish, brown. It is transparent, to translucent. The hardness is 4-5. The density is 4900-5200 kilograms per cubic metre. It is the characteristic mineral of the hydrothermal deposits, which are associated with the sub-alkaline rocks and carbonatites. It may be found with barite, calcite, fluorite.

The secondary forming of bastnäsite is associated with the destruction of the rare-earth silicates, especially of allanite of the pegmatitic veins. Bastnäsite is the main raw material source for the obtainment of cerium and its compounds. The largest deposit is the Mountain Pass (USA). It is beneficiated by the gravity methods; in case of the fine interspersion, by the flotation with the usage of the fatty acids.