bastnäsite

{{Infobox mineral | name = Bastnäsite, bastnaesite | category = Carbonate mineral | boxwidth = | boxbgcolor = | image = Bastnaesit Burundi.jpg | imagesize = | caption = Bastnäsite from Gakara Burundi | formula = (La, Ce, Y)CO3F |IMAsymbol=Bsn | strunz = 5.BD.20a | system = Hexagonal | class = Ditrigonal dipyramidal (m2) H-M symbol: ( m2) | symmetry = P2c | unit cell = a = 7.118(1) Å, c = 9.762(1) Å; Z = 6 (bastnäsite-(Ce)) | color = Honey-yellow, reddish brown | habit = Tabular to equant striated crystals, deep grooves may resemble thin plates stack, oriented overgrowths, also granular, massive | twinning = Dauphine law, Brazil law and Japan law | cleavage = Imperfect to indistinct on {100}, parting on {0001} | fracture = Uneven | tenacity = Brittle | mohs = 4–5 | luster = Vitreous, greasy, pearly on basal partings | refractive = nω = 1.717–1.722 nε = 1.818–1.823 | opticalprop = Uniaxial (+) | birefringence = δ = 0.101 max. | pleochroism = Faint, E > O, colorless to pale yellow or orange | streak = White | gravity = 4.95–5.0 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = Strongly piezoelectric; dark red cathodoluminescence, 25px Radioactive if uranium and/or thorium-rich | references = }}

The mineral bastnäsite (or bastnaesite) is one of a family of three fluorocarbonate minerals, which includes bastnäsite-(Ce) with a formula of (Ce, La)CO3F, bastnäsite-(La) with a formula of (La, Ce)CO3F, and bastnäsite-(Y) with a formula of (Y, Ce)CO3F. Some of the bastnäsites contain OH− instead of F− and receive the name of hydroxylbastnasite. Most bastnäsite is bastnäsite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnäsite and the phosphate mineral monazite are the two largest sources of cerium and other rare-earth elements.