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Betafite
Betafite
	Betafite dodecahedron, Locality: Bancroft, Ontario, Canada
General
Category	Oxide minerals
Formula; (repeating unit)	(Ca,U)2(Ti,Nb,Ta)2O6(OH)
IMA symbol	Btf
Strunz classification	4.DH.15
Crystal system	Cubic
Space group	Fd3m (no. 227)
Identification
Color	Brown, Black, Brownish green, Yellow, Greenish black
Crystal habit	Massive - Granular
Cleavage	None
Mohs scale hardness	5 - 5.5
Luster	Vitreous
Streak	Yellowish white
Diaphaneity	Translucent to Opaque
Density	3.7 - 4.9
Other characteristics	Radioactive 17.2% (U)
References

Betafite is a mineral group in the pyrochlore supergroup, with the chemical formula (Ca,U)₂(Ti,Nb,Ta)₂O₆(OH). Betafite typically occurs as a primary mineral in granite pegmatites, rarely in carbonatites. Originally defined by the B-site atom Ti,^[5] the development of new nomenclature for mineral names^[6] 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^[7] are presently retained.^[5] They are oxyuranobetafite and oxycalciobetafite. The term betafite is now a synonym or varietal group name under the pyrochlore super group.^[8]

Structure

The pyrochlore supergroup minerals conform to the general formula, A_2−mB₂X_6−wY_1−n, where the m, w, and n variables represent the parameters that indicate incomplete occupancy of the A, Y, and X sites.^[5] They crystallize isometric system with a space group of Fd3m or its subgroups where Betafite has a hexoctahedral class.^[7] 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,^[5] 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, magnetite, sodalite and rare biotite. While with SEM-EDS, titanite, apatite, and baddeleyite were also observed.^[9] While the occurrence of oxycalciobetafite on the moon has been rather difficult to ascertain, occurrences of oxyuranobetafite have been described.^[10]

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.^[11]^[12] The depletion of uraninite rich ore bodies has led to the search and mild application of refractory uranium minerals as a source of uranium to keep up with the increasing demands.^[2]

References

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
^ ^a ^b Prinz, Martin; Harlow, George; Peters, Joseph, eds. (1978). "Oxides and Hydroxides". Simon & Schuster's guide to rocks and minierals. New York: Simon & Schuster, Inc. ISBN 978-0671244170.
^ "Betafite mineral data". Mindat.org. Retrieved 2 July 2022.
^ Barthelmy, David (2014). "Betafite Mineral Data". Webmineral.com. Retrieved 2 July 2022.
^ ^a ^b ^c ^d Atencio, D.; Andrade, M. B.; Christy, A. G.; Giere, R.; Kartashov, P. M. (1 June 2010). "The pyrochlore supergroup of minerals: Nomenclature". The Canadian Mineralogist. 48 (3): 673–698. Bibcode:2010CaMin..48..673A. doi:10.3749/canmin.48.3.673.
^ Hatert, F.; Burke, E. A.J. (1 June 2008). "The Ima-CNMNC Dominant-Constituent Rule Revisited and Extended". The Canadian Mineralogist. 46 (3): 717–728. Bibcode:2008CaMin..46..717H. doi:10.3749/canmin.46.3.717. hdl:2268/77775.
^ ^a ^b Hogarth, D.D. (1977). "Classification and nomenclature of the pyrochlore group" (PDF). American Mineralogist. 62: 403–410. Retrieved 2 July 2022.
^ Christy, A. G.; Atencio, D. (February 2013). "Clarification of status of species in the pyrochlore supergroup". Mineralogical Magazine. 77 (1): 13–20. Bibcode:2013MinM...77...13C. doi:10.1180/minmag.2013.077.1.02. S2CID 65081781.
^ Cámara, F.; Williams, C. T.; Della Ventura, G.; Oberti, R.; Caprilli, E. (December 2004). "Non-metamict betafite from Le Carcarelle (Vico volcanic complex, Italy): occurrence and crystal structure". Mineralogical Magazine. 68 (6): 939–950. Bibcode:2004MinM...68..939C. doi:10.1180/0026461046860224. S2CID 56337945.
^ Mokhov, A. V.; Kartashov, P. M.; Bogatikov, O. A.; Ashikhmina, N. A.; Magazina, L. O.; Koporulina, E. V. (October 2008). "Fluorite, hatchettolite, calcium sulfate, and bastnasite-(Ce) in the lunar regolith from Mare Crisium". Doklady Earth Sciences. 422 (1): 1178–1180. Bibcode:2008DokES.422.1178M. doi:10.1134/S1028334X08070416. S2CID 129454847.
^ Turner, H.W. (1928). "Review of the Radioactive Minerals of Madagascar". Economic Geology. 23 (1): 62–84. Bibcode:1928EcGeo..23...62T. doi:10.2113/gsecongeo.23.1.62.
^ Lumpkin, Gregory R.; Ewing, Rodney C. (1 October 1996). "Geochemical alteration of pyrochlore group minerals; betafite subgroup". American Mineralogist. 81 (9–10): 1237–1248. Bibcode:1996AmMin..81.1237L. doi:10.2138/am-1996-9-1022. S2CID 201092881.