Betafite is a mineral group in the

pyrochlore Pyrochlore () is a mineral group of the niobium end member of the pyrochlore supergroup. Pyrochlore is also a term for the crystal structure ''F''dm. The name is from the Greek , ''fire'', and , ''green'' because it typically turns green on ignit ...

supergroup, with the chemical formula . Betafite typically occurs as a primary mineral in

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

pegmatites A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...

, rarely in

carbonatite Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...

s. Originally defined by the B-site atom Ti, the development of new nomenclature for mineral names led to modernization of the system for nomenclature of pyrochlore and betafite in order to further rationalize the naming process of this grouping of minerals. Only two of the mineral species that were formerly recognized as betafite are presently retained. They are ''oxyuranobetafite'' and ''oxycalciobetafite''. The term ''betafite'' is now a synonym or varietal group name under the pyrochlore super group.

Structure

The pyrochlore supergroup minerals conform to the general formula, A_2−''m''B₂X_6−''w''Y_1−''n'', where the ''m'', ''w'', and ''n'' variables represent the parameters that indicate incomplete occupancy of the A, Y, and X sites. They crystallize isometric system with a space group of Fdm or its subgroups where Betafite has a hexoctahedral class. Site A is generally an 8-coordinated cation with a ~1.0 Å radius, B site is generally a 6-coordinated cation, which contains the elements Ti, Nb, and Ta usually for betafite, site X is generally O but can subjugate to OH and F, and site Y is typically an anion but can also be a vacancy, H₂O, or a very large monovalent cation, like Cs, K, and Rb.

Origin and uses

Oxycalciobetafite occurs in the

pyroclastic Pyroclast, Pyroclastic or Pyroclastics may refer to: Geology * Pyroclast, or airborne volcanic tephra fragments * Pyroclastic rock, rock fragments produced and ejected by explosive volcanic eruptions * Pyroclastic cone, landform of ejecta fro ...

formation belonging to the main effusive stage of the Vico activity where it is contained within foid-bearing

syenite Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). It is considered a amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

sodalite Sodalite ( ) is a tectosilicate mineral with the formula , with royal blue varieties widely used as an ornamental gemstone. Although massive sodalite samples are opaque, crystals are usually transparent to translucent. Sodalite is a member of th ...

and rare

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

. While with SEM-EDS,

titanite Titanite, or sphene (), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly rep ...

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

, and

baddeleyite Baddeleyite is a rare zirconium oxide mineral (ZrO2 or zirconia), occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high Index of refraction, indices of refraction, and ranges from colorless to yel ...

were also observed. While the occurrence of oxycalciobetafite on the moon has been rather difficult to ascertain, occurrences of oxyuranobetafite have been described. Though there is no use as of yet for the accepted betafite species, the pyrochlore super-group that contains the former betafites are potential sources of uranium, thorium, and niobium. The depletion of uraninite rich ore bodies has led to the search and mild application of refractory uranium minerals as a source of

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

to keep up with the increasing demands.

References

External links

* Uranium minerals Titanium minerals Niobium minerals Tantalum minerals Calcium minerals Oxide minerals Cubic minerals Minerals in space group 227 Minerals described in 1912 {{oxide-mineral-stub