Chemistry:Thorianite

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Thorianite
Thorianite-54888.jpg
Group of interpenetrating twinned thorianite crystals from Ambatofotsy, Madagascar (size: 1.6 x 1.4 x 1.3 cm)
General
CategoryOxide mineral
Formula
(repeating unit)		Thorium oxide, ThO2
Strunz classification4.DL.05
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFm3m
Unit cella = 5.595 Å; Z = 4
Identification
ColorDark gray, brown-black
Crystal habitCubic crystals, usually rounded to some degree in detrital deposits
TwinningPenetration twins on {111} common
CleavagePoor/Indistinct
FractureIrregular to uneven, sub-conchoidal
Mohs scale hardness6.5 – 7
|re|er}}Resinous, sub-metallic
StreakGrey, grey green to black
DiaphaneityOpaque, translucent on thin edges
Specific gravity9.7
Optical propertiesIsotropic
Refractive indexn = 2.20 – 2.35
Other characteristicsRadioactive.svg Radioactive
References[1][2][3]

Thorianite is a rare thorium oxide mineral, ThO2.[5] It was originally described by Ananda Coomaraswamy in 1904 as uraninite,[6] but recognized as a new species by Wyndham R. Dunstan.[7] It was so named by Dunstan on account of its high percentage of thorium; it also contains the oxides of uranium, lanthanum, cerium, praseodymium and neodymium. Helium is present, and the mineral is slightly less radioactive than pitchblende,[8] but is harder to shield due to its high energy gamma rays. It is common in the alluvial gem-gravels of Sri Lanka, where it occurs mostly as water worn, small, heavy, black, cubic crystals. The largest crystals are usually near 1.5 cm. Larger crystals, up to 6 cm (2.4 in), have been reported from Madagascar .

Chemistry

Based on color, specific gravity and composition three types of thorianite are distinguished:[9]

  • α-thorianite
  • β-thorianite
  • γ-thorianite

Thorianite and uraninite form a complete solid solution series in synthetic and natural material.[10] The division between the two species is at Th:U = 1:1 with U possibly making up to 46.50% and Th ranging up to 87.88%.[11] Rare earths, chiefly Ce, substitute for Th in amounts up to 8% by weight.[10][12] Ce is probably present as Ce4+. Complete series is known in synthetic material between CeO2 - PrO2 - ThO2 - UO2. Small amounts of Fe3+ and Zr also may be isomorphous with Th. Pb present is probably radiogenic.

Varieties

  • Aldanite – a variety of thorianite containing 14.9% to 29.0% UO2 and 11.2% to 12.5% PbO.[13]
  • Uranothorianite[14]
  • Thorianite Cerian[15][16]
  • Thorianite La bearing[15]

Occurrence

Usually found in alluvial deposits, beach sands, heavy mineral placers, and pegmatites.

  • Sri Lanka – In stream gravels, Galle district, Southern Province; Balangoda district; near Kodrugala, Sabaragamuwa Province; and from a pegmatite in Bambarabotuwa area.
  • India – Reported from beach sands of Travancore (Kerala).[17]
  • Madagascar – Found in alluvial deposits of Betroka and Andolobe.[18] Also as very large crystals from Fort Dauphin; at Andranondambo and other localities.
  • Russia – In black sands of a gold placer on Boshogoch River, Transbaikalia, Siberia; in the Kovdor Massif by Kovdor, Kola Peninsula; in the Yenisei Range, Siberia.
  • United States – reported from Easton, Pennsylvania; black sands in Missouri River, near Helena, Montana; Scott River, Siskiyou County, California ;[19] black sands in Nixon Fork and Wiseman districts, Alaska.[20][21]
  • Canada – Reported with uraninite in a pegmatite on Charlebois Lake, east of Lake Athabasca;[22] Uranon variety reported from pegmatite and metesomatized zones in crystalline limestones from many locations in Quebec and Ontario.[23]
  • South Africa – Occurs with baddeleyite as an accessory in carbonatite at Phalaborwa, Eastern Transvaal.[24]
  • Democratic Republic of Congo - Kasaï region[25]

See also

References

  1. ↑ "Handbook of Mineralogy". http://www.handbookofmineralogy.com/pdfs/thorianite.pdf. 
  2. ↑ Mindat.org
  3. ↑ Webmineral data
  4. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W. 
  5. ↑ Frondel, C. (1958). Systematic Mineralogy of Uranium and Thorium. United States Government Printing Office. 
  6. ↑ Coomaraswamy, A.K. (1904). "Uraninite". Spolia Zeylanica Pt. 6 (2): 57. 
  7. ↑ Dunstan, Wyndham R. (1904-03-31). "The occurrence of Thorium in Ceylon". Nature 69 (1796): 510–511. doi:10.1038/069510d0. Bibcode: 1904Natur..69..510D. https://zenodo.org/record/1429437. 
  8. ↑  One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed (1911). "Thorianite". Encyclopædia Britannica. 26 (11th ed.). Cambridge University Press. p. 878. 
  9. ↑ Kobayashi, M. (1912). "On the composition of thorianite". Tohoku Imp. Univ. Sci. Repts. 1 (Ist Ser): 201–206. 
  10. ↑ 10.0 10.1 Palache, C.; H. Berman; C. Frondel (1944). Dana's System of Mineralogy, Volume 1. John Wiley and Sons, New York. pp. 620–622. 
  11. ↑ Heinrich, E. W. (1958). Mineralogy and Geology of Radioactive Raw Materials. McGraw-Hill. 
  12. ↑ Graham, A. R. (1955). "CERIANITE CeO2: A NEW RARE-EARTH OXIDE MINERAL". Am. Mineral. 40. 
  13. ↑ Bespalov, M.M. (1941). "On discovery of a new mineral of the thorianite group [in Russian]". Sovietskaya Geologiya II (6): 105–107. 
  14. ↑ "Uranothorianite mineral information and data". http://www.mindat.org/min-4114.html. Retrieved 2007-06-28. 
  15. ↑ 15.0 15.1 "Minerals with crystal structure determined". Archived from the original on 2007-09-27. https://web.archive.org/web/20070927022021/http://sdpd.univ-lemans.fr/minknown.html#T. Retrieved 2007-06-27. 
  16. ↑ "ICSD for WWW : Details (Thorianite Cerian)". http://icsdweb.fiz-karlsruhe.de/details.php?id%5B%5D=24439&PHPSESSID=734118bb8. Retrieved 2007-06-27. 
  17. ↑ Viswanathan, P. (1953). "Thorianite in Travancore". Mineral. Mag. 88: 282. 
  18. ↑ Lacroix, A. (1923). Minéralogie de Madagascar. Augustin Challamel, éditeur, Librairie maritime et coloniale. https://archive.org/details/MineralogieDeMadagascarTome3. 
  19. ↑ George, D'Arcy (1949). "Mineralogy of Uranium and Thorium Bearing Minerals". USAEC Technical Information Service, Oak Ridge, Tennessee. RMO-563: 198. 
  20. ↑ White, M. G. (1952). Radioactivity of Selected Rocks and Placer Concentrates from Northeastern Alaska. GS-C-195, Geological Survey. 
  21. ↑ White, M. G.; J. M. Stevens (1953). Reconnaissance For Radioactive Deposits In The Ruby-Poorman District, Ruby Quadrangle, Central Alaska,1949. TEI-192, Geological Survey. 
  22. ↑ Lang, A. H.; J. W. Griffith; H. R. Steacy (1962). Canadian Deposits of Uranium and Thorium. Geological Survey of Canada. 
  23. ↑ Robinson, S. C.; A. P. Sabina (1955). "Uraninite And Thorianite From Ontario And Quebec". Am. Mineral. 40. 
  24. ↑ Hiemstra, S. A. (1955). "Baddeleyite from Phalaborwa, Eastern Transvaal". American Mineralogist 40: 275–282. 
  25. ↑ Ledoux, A.. "Les roches cristallines du Kasai". Soc. Geol. Belgique Annales 40: C177. 

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