betafite
{{Short description|Mineral group}}
{{Infobox mineral
| name = Betafite
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| boxbgcolor =#73604c
| image = Betafite_octahedron.jpg
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| caption = Betafite dodecahedron, Locality: Bancroft, Ontario, Canada
| category = Oxide minerals
| formula = (Ca,U)2(Ti,Nb,Ta)2O6(OH)
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| strunz = 4.DH.15
| dana =
| system = Cubic
| symmetry = Fd{{overline|3}}m (no. 227)
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| color =Brown, Black, Brownish green, Yellow, Greenish black
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| habit =Massive - Granular
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| cleavage =None
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| mohs = 5 - 5.5
| luster = Vitreous
| streak =Yellowish white
| diaphaneity =Translucent to Opaque
| gravity =
| density =3.7 - 4.9
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| other = 25px Radioactive 17.2% (U)
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| references = {{cite book |editor1-last=Prinz |editor1-first=Martin |editor2-last=Harlow |editor2-first=George |editor3-last=Peters |editor3-first=Joseph |title=Simon & Schuster's guide to rocks and minierals |date=1978 |isbn=978-0671244170 |chapter=Oxides and Hydroxides|location=New York |publisher=Simon & Schuster, Inc.}}{{mindat|id=649|title=Betafite mineral data|access-date=2 July 2022}}{{Cite web|last1=Barthelmy|first1=David|year=2014|url=http://webmineral.com/data/Betafite.shtml|access-date=2 July 2022|title = Betafite Mineral Data|website=Webmineral.com}}
}}
Betafite is a mineral group in the pyrochlore supergroup, with the chemical formula {{Chem2|(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, the development of new nomenclature for mineral names{{cite journal |last1=Hatert |first1=F. |last2=Burke |first2=E. A.J. |title=The Ima-CNMNC Dominant-Constituent Rule Revisited and Extended |journal=The Canadian Mineralogist |date=1 June 2008 |volume=46 |issue=3 |pages=717–728 |doi=10.3749/canmin.46.3.717|bibcode=2008CaMin..46..717H |hdl=2268/77775 }} 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.{{cite journal |last1=Christy |first1=A. G. |last2=Atencio |first2=D. |title=Clarification of status of species in the pyrochlore supergroup |journal=Mineralogical Magazine |date=February 2013 |volume=77 |issue=1 |pages=13–20 |doi=10.1180/minmag.2013.077.1.02|bibcode=2013MinM...77...13C |s2cid=65081781 }}
Structure
The pyrochlore supergroup minerals conform to the general formula, A2−mB2X6−wY1−n, where the m, w, and n variables represent the parameters that indicate incomplete occupancy of the A, Y, and X sites.{{cite journal |last1=Atencio |first1=D. |last2=Andrade |first2=M. B. |last3=Christy |first3=A. G. |last4=Giere |first4=R. |last5=Kartashov |first5=P. M. |title=The pyrochlore supergroup of minerals: Nomenclature |journal=The Canadian Mineralogist |date=1 June 2010 |volume=48 |issue=3 |pages=673–698 |doi=10.3749/canmin.48.3.673|bibcode=2010CaMin..48..673A }} They crystallize isometric system with a space group of Fd{{overline|3}}m or its subgroups where Betafite has a hexoctahedral class.{{cite journal |last1=Hogarth |first1=D.D. |year=1977 |title=Classification and nomenclature of the pyrochlore group |journal=American Mineralogist |volume=62 |pages=403–410 |url=http://www.minsocam.org/ammin/am62/am62_403.pdf |access-date=2 July 2022}} 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, magnetite, sodalite and rare biotite. While with SEM-EDS, titanite, apatite, and baddeleyite were also observed.{{cite journal |last1=Cámara |first1=F. |last2=Williams |first2=C. T. |last3=Della Ventura |first3=G. |last4=Oberti |first4=R. |last5=Caprilli |first5=E. |title=Non-metamict betafite from Le Carcarelle (Vico volcanic complex, Italy): occurrence and crystal structure |journal=Mineralogical Magazine |date=December 2004 |volume=68 |issue=6 |pages=939–950 |doi=10.1180/0026461046860224|bibcode=2004MinM...68..939C |s2cid=56337945 }} While the occurrence of oxycalciobetafite on the moon has been rather difficult to ascertain, occurrences of oxyuranobetafite have been described.{{cite journal |last1=Mokhov |first1=A. V. |last2=Kartashov |first2=P. M. |last3=Bogatikov |first3=O. A. |last4=Ashikhmina |first4=N. A. |last5=Magazina |first5=L. O. |last6=Koporulina |first6=E. V. |title=Fluorite, hatchettolite, calcium sulfate, and bastnasite-(Ce) in the lunar regolith from Mare Crisium |journal=Doklady Earth Sciences |date=October 2008 |volume=422 |issue=1 |pages=1178–1180 |doi=10.1134/S1028334X08070416|bibcode=2008DokES.422.1178M |s2cid=129454847 }}
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.{{cite journal |last1=Turner |first1=H.W. |year=1928 |title=Review of the Radioactive Minerals of Madagascar |journal=Economic Geology |volume=23 |issue=1 |pages=62–84|doi=10.2113/gsecongeo.23.1.62 |bibcode=1928EcGeo..23...62T }}{{cite journal |last1=Lumpkin |first1=Gregory R. |last2=Ewing |first2=Rodney C. |title=Geochemical alteration of pyrochlore group minerals; betafite subgroup |journal=American Mineralogist |date=1 October 1996 |volume=81 |issue=9–10 |pages=1237–1248 |doi=10.2138/am-1996-9-1022|bibcode=1996AmMin..81.1237L |s2cid=201092881 }} 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.
References
{{Reflist}}
External links
- {{Commons category-inline}}
{{Titanium minerals}}
Category:Minerals in space group 227
Category:Minerals described in 1912
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