Fluocerite, also known as tysonite, is a mineral consisting of

cerium Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the +3 o ...

and

lanthanum Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. It is the eponym of the lanthanide series, a group of 15 similar elements between lantha ...

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts typ ...

s, with the chemical formula . The end members are classified as two different mineral types depending on the

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

, fluocerite-(Ce) and fluocerite-(La), corresponding respectively to

lanthanum trifluoride Lanthanum trifluoride is a refractory ionic compound of lanthanum and fluorine. The LaF3 structure Bonding is ionic with lanthanum highly coordinated. The cation sits at the center of a trigonal prism. Nine fluorine atoms are close: three at ...

and

cerium trifluoride Cerium(III) fluoride (or cerium trifluoride), CeF3, is an ionic compound of the rare earth metal cerium and fluorine. It appears as a mineral in the form of fluocerite-(Ce) - a very rare mineral species related mainly to pegmatites and rarely t ...

. Both crystallize in the trigonal system. Fluocerite-(Ce) was first described (without the Ce) in 1845 from

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

veins in

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...

. Fluocerite-(La) was first described in 1969 from the type locality in central

Kazakhstan Kazakhstan, officially the Republic of Kazakhstan, is a transcontinental country located mainly in Central Asia and partly in Eastern Europe. It borders Russia to the north and west, China to the east, Kyrgyzstan to the southeast, Uzbeki ...

. The name tysonite was given in 1880 to the same type of mineral found in Colorado. Tysonite-type structure is used for rare-earth fluorides with the P3c1

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...

structure.

References

Lanthanide minerals Trigonal minerals Minerals in space group 165 Fluorine minerals {{halide-mineral-stub