Betafite is a mineral group in the

pyrochlore Pyrochlore () is a mineral group of the niobium end member of the pyrochlore supergroup. The general formula, (where A and B are metals), represent a family of phases isostructural to the mineral pyrochlore. Pyrochlores are an important class of ...

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

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 co ...

, rarely in

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

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 formation belonging to the main effusive stage of the Vico activity where it is contained within foid-bearing syenite, which also holds optical observances of K-feldspar, and minor amphibole,

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...

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 t ...

and rare biotite. While with SEM-EDS,

titanite Titanite, or sphene (from the Greek ''sphenos'' (σφηνώ), meaning wedge), 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 ...

, apatite, and baddeleyite 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 with the 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. Uranium is weak ...

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