Thorianite

Last updated
Thorianite
Thorianite-54888.jpg
Group of interpenetrating twinned thorianite crystals from Ambatofotsy, Madagascar (size: 1.6 x 1.4 x 1.3 cm)
General
Category Oxide mineral
Formula Thorium oxide, ThO2
IMA symbol Tho [1]
Strunz classification 4.DL.05
Crystal system Isometric
Crystal class Hexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space group Fm3m
Unit cell a = 5.595 Å; Z = 4
Identification
ColorDark gray, brown-black
Crystal habit Cubic crystals, usually rounded to some degree in detrital deposits
Twinning Penetration twins on {111} common
Cleavage Poor/Indistinct
Fracture Irregular to uneven, sub-conchoidal
Mohs scale hardness6.5 – 7
Luster Resinous, sub-metallic
Streak Grey, grey green to black
Diaphaneity Opaque, translucent on thin edges
Specific gravity 9.7
Optical propertiesIsotropic
Refractive index n = 2.20 – 2.35
Other characteristics Radioactive.svg Radioactive
References [2] [3] [4]

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.

Contents

Chemistry

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

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 uranium possibly making up to 46.50% and thorium ranging up to 87.88%. [11] Rare earths, chiefly cerium, substitute for thorium in amounts up to 8% by mass. [10] [12] Cerium is probably present as Ce4+. Complete series is known in synthetic material between CeO2 - PrO2 - ThO2 - UO2. Small amounts of Fe3+ and zirconium also may be isomorphous with thorium. Lead present is probably radiogenic.

Varieties

Occurrence

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

See also

References

  1. ↑ 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.
  2. ↑ "Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2011-12-10.
  3. ↑ Mindat.org
  4. ↑ Webmineral data
  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. Bibcode:1904Natur..69..510D. doi:10.1038/069510d0. S2CID   4032255.
  8. ↑ Wikisource-logo.svg One or more of the preceding sentences incorporates text from a publication now in the public domain :  Chisholm, Hugh, ed. (1911). "Thorianite". Encyclopædia Britannica . Vol. 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. 1 2 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" . Retrieved 2007-06-28.
  15. 1 2 "Minerals with crystal structure determined". Archived from the original on 2007-09-27. Retrieved 2007-06-27.
  16. ↑ "ICSD for WWW : Details (Thorianite Cerian)" . Retrieved 2007-06-27.[ permanent dead link ]
  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.
  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" (PDF). USGS Report. TEI-192, Geological Survey: 62. Bibcode:1953usgs.rept...62W. doi:10.3133/tei192.
  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.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.